Study Guide for

Linux System Administration 1

Lab work for LPI 101

version 0.2

released under the GFDL by LinuxIT

Copyright (c) 2005 LinuxIT.

Permission is granted to copy, distribute and/or modify this document

under the terms of the GNU Free Documentation License, Version 1.2

or any later version published by the Free Software Foundation;

with the Invariant Sections being History, Acknowledgements, with the	Front-Cover Texts being “released under the GFDL by LinuxIT”.

see full license agreement on p.164

Introduction:

Acknowledgments

The original material was made available by LinuxIT's technical training centre www.linuxit.com. Many thanks to Andrew Meredith for suggesting the idea in the first place. A special thanks to all the students who have helped dilute the technical aspects of Linux administration through their many questions, this has led to the inclusion of more illustrations attempting to introduce concepts in a user friendly way. Finally, many thanks to Paul McEnery for the technical advice and for starting off some of the most difficult chapters such as the ones covering the X server (101), modems (102) and the Linux kernel (102).

The manual is available online at http://savannah.nongnu.org/projects/lpi-manuals/. Thank you to the Savannah Volunteers for assessing the project and providing us with the Web space.

History

First release (version 0.0) October 2003. Reviewed by Adrian Thomasset.

Revised January 2004 after review by Andrew Meredith.

November 2004. Section on expansion cards added in 'Hardware Configuration' chapter by Adrian Thomasset

December 2004. Index and mapped objectives added by Adrian Thomasset.

January 2005. Glossary of terms, command and file review added at end of chapters by Adrian Thomasset

June 2005. Added new entries in line with recommendations from SerNet for the LATM process, by Andrew Meredith with additional text supplied by Andrew D Marshall and review by Adrian Thomasset. Section on Debian tools supplied by Duncan Thomson.

August 2005. "Linux System Administration 1 - Lab work LPI 101 - version 0.2" has been awarded the LATM status by SerNet.

Dramatis Personi

Adrian Thomasset	<adriant@linuxit.com>	http://www.linuxit.com/

Andrew Meredith	<andrew@anvil.org>	http://www.anvil.org/

Andrew D Marshall	<admarshall@gmail.com>	http://h0lug.sourceforge.net/

Duncan Thomson	<thom-ci0@paisley.ac.uk>	http://www.paisley.ac.uk/

Goals

This manuals primary aim is to provide explanations, examples and exercises for those preparing for the Linux Professional Institute (LPI) Certification Programme 1 (LPIC-1), Exam 101.

Three core sources of criteria guide this manual to its primary goals:

The LPI's Exam-101 "Objectives".

Its LPI-Approved Training Materials (LATM) criteria.

The Linux Documentation Project (LDP or TLDP) Author Guide (AG).

The LPI's Exam-101 Objectives and LATM criteria are summarized below. The Objectives are also online at:
http://www.lpi.org/en/obj_101.html

The LDP Author Guide [http://www.tldp.org/LDP/LDP-Author-Guide/] provides a consistent, comprehensive set of guidelines for those wanting to publish HOWTOs, Tutorials and Manuals via the world's largest GNU/Linux documentation system, the LDP.

This manual adopts as its second prime objective, on equal footing with its first, the LDP Author Guide's challenge to prospective LDP authors, "to massage all of the raw data into a readable, entertaining and understandable whole." [LDP-AG, 4.1. Writing the Text]

Intended Training Schedules

The content herein is designed to accompany practical courses preparing for the LPI 101 exam of the LPIC-1 programme. While this material was generally structured to work with a course of 24-32 hours in consecutive 8-hour sessions, it is modularized to also work for shorter or longer sessions, consecutive or otherwise.

Intended Audience & Prerequisites

This manual's material assumes its users will already have:

Extensive experience (several years) using Intel x86 computers, including a strong knowledge of hardware components and their interaction with basic operating system (OS) components.

A general knowledge of computing and networking basics such as binary and hexadecimal maths, common units of measure (bytes, KB vs Kb, Mhz, etc), file-system structures, Ethernet and Internet networking operations and hardware, etc.

More than three cumulative months of practical experience using a GNU/Linux, BSD or Unix OS, logged in and working at the command-line (in a text terminal or console) either locally or remotely.

Those with less experience, however, should not be discouraged from using this manual, if (and only if) they are willing to spend extra time catching up on the prerequisite background skills and knowledge; a challenging task, but not an impossible one.

Further references and examples are provided for the various uses of commands, as well as exercises and accompanying answers demonstrating exam-like problem-solving. All are optional with those most recommended either discussed or referenced in the manual's body.

The LPI Certification Program

There are currently two LPI certification levels. The first level LPIC-1 is granted after passing both exams LPI 101 and LPI 102. Similarly passing the LPI 201 and LPI 202 exams will grant the second level certification LPIC-2.

There are no certification pre-requisites for LPI 101 and 102. However the exams for LPIC-2 can only be attempted once LPIC-1 has been obtained.

Instructor Notice

There are no instructor notes with this manual. The following issues must be considered.

The exercises in the sections Managing Devices and The Linux Filesystem both assume that a new partition can be created. Make sure during the installation that a large extended partition with at least 100MB free space is available after all the partitions have been created.

The following RPM packages are needed for the exercises:

rpm-build

sharutils

No Guarantee

The manual comes with no guarantee at all.

Resources

www.lpi.org

www.linux-praxis.de

www.lpiforums.com

www.tldp.org

www.fsf.org

www.linuxit.com

Notations

Commands and filenames will appear in the text in bold.

The <> symbols are used to indicate a non optional argument.

The [] symbols are used to indicate an optional argument

Commands that can be typed directly in the shell are highlighted as below

command

or

command

Introduction:	iii

Acknowledgments	iii

History	iii

Dramatis Personi	iii

Goals	iii

Intended Training Schedules	iv

Intended Audience & Prerequisites	iv

The LPI Certification Program	iv

Instructor Notice	iv

No Guarantee	iv

Resources	iv

Notations	v

Installation	1

1. The Installation CD	2

2. Local Installations	3

3. Network Installation	3

4. Rescue disk	4

5. Partitioning Schemes	5

6. Easy Dual Booting	6

7. Exercises and Summary	8

Hardware Configuration	10

1. Resource Allocation	11

2. PC Expansion Cards	12

3. USB Support	13

4. SCSI Devices	14

5. Network cards	15

6. Setting up modems	16

7. Printer Configuration	21

8. Sound Cards	22

9. Exercises and Summary	24

Managing Devices	27

1. Disks and Partitions	28

2. Partitioning Tools:	30

3. Bootloaders	31

4. Managed devices	33

5. Quotas	35

6. Exercises and Summary	36

The Linux Filesystem	39

1. The Filesystem Structure	40

2. Formatting and File System Consistency	42

3. Monitoring Disk Usage	45

4. File Permissions and Attributes	46

5. Exercises and Summary	52

The Command Line	56

1. The interactive shell	57

2. Variables	58

3. Input, Output, Redirection	59

4. Metacharacters and Quotes	62

5. The Command History	63

6. Other Commands	64

7. Exercise and Summary	67

File Management	71

1. Moving around the filesystem	72

2. Finding Files and Directories	72

3. Handling directories	74

4. Using cp and mv	74

5. Hard Links and Symbolic Links	75

7. Touching and dd-ing	76

8. Exercises and Summary	78

Process Management	81

1. Viewing running processes	82

2. Modifying Processes	83

3. Processes and the shell	85

4. Exercises and Summary	87

Text Processing	90

1. cat the Swiss Army Knife	91

2. Simple tools	92

3. Manipulating text	94

4. Exercises and Summary	97

Software Installation	99

1. Introduction	100

2. Static and Shared Libraries	101

3. Source Distribution Installation	105

4. The RedHat Package Manager RPM	108

5. Debian Package Management	113

6. The Alien Tool	117

7. Exercises and Summary	118

Advanced Text Manipulation	121

1. Regular Expressions	122

2. The grep family	122

3. Working with grep	123

4. egrep and fgrep	123

5. The Stream Editor - sed	124

6. Exercises and Summary	126

Using vi	128

1. vi Modes	129

2. Text Items	129

3. Inserting Text	130

4. Cut and Paste	130

5. Copy Paste	131

6. Search and Replace	131

7. Undo and Redo	132

8. Running a Shell Command	132

9. Save and Quit	132

10. Exercises and Summary	133

The X Environment	135

1. Introduction	136

2. Configuring X11R6	137

3. Controlling X clients	139

4. Starting X	140

5. The Display Manager	141

6. Troubleshooting X Clients	145

7. Choosing a Window Manager	145

9. Exercises and Summary	146

Answers to Revision Questions	150

LPI 101 Objectives	152

Topic 101: Hardware & Architecture	152

Topic 102: Linux Installation & Package Management	154

Topic 103: GNU & Unix Commands	156

Topic 104: Devices, Linux Filesystems, Filesystem Hierarchy Standard	159

Topic 110: The X Window System	162

GNU Free Documentation License	164

INDEX	169

Installation

Prerequisites

None

Goals

Understand the layout of a typical Linux installation CD

Perform different types of installations

Create a simple partition scheme (see also p.28)

Contents

Installation	1

1. The Installation CD	2

2. Local Installations	3

3. Network Installation	3

4. Rescue disk	4

5. Partitioning Schemes	5

6. Easy Dual Booting	6

7. Exercises and Summary	8

1. The Installation CD

The various Linux distributions have different names for the directories on the installation CD. The generic structure of the CDROM is as follows:

Generic Installation CD layout
cdrom packages images dosutils

packages: This directory contains the pre-compiled packages. Here are the associated names for the main distrubutions:

debian: dist

mandrake: Mandrake

redhat: RedHat

suse: suse

Initially all the software installed on the system comes from these packaged files. See the section on package managers on p.108 for more details.

images: This directory contains various “images”. These are special flat files often containing directory structures. An initial ramdisk (initrd) is an example of an image file. There are different types of images necessary to:

- boot the installation process

- provide additional kernel modules

- rescue the system

Some of these files can be copied to a floppy disk when the installation is started using floppies rather than the CDROM. The Linux tool used to do this is dd. There is a tool called rawrite which does the same under DOS.

The image is a special file which may contain subdirectories (much like an archive file).

Image file structure
DIR1 Image file DIR2

An image file can be mounted on a loop device. If the image file name is called Image then the following command will allow one to view the content of this file in the /mnt/floppy directory:

mount -o loop /path/to/Image /mnt/floppy

dosutils: this directory contains DOS tools which may be used to prepare a Linux installation such as the

rawrite.exe tool mentioned above. Another tool is the fips utility which non destructively partions a C:\ drive in two provided the underlying filesystem type is FAT and not NTFS.

2. Local Installations

The easiest and most common type of installation is a local installation. Most distributions are a CD iso image with an automatic installation script. On machines with no CD-ROM hardware it is still possible to start an installation from a floppy.

CD-ROM installation

Change the settings in the BIOS for the computer to boot from CD. The installation is menu driven and allows for advanced and basic configuration.

Floppy Installation

If for some reason you don't boot using the CD-ROM you will need to create a floppy installation image. This can happen if the CD is not bootable or you have downloaded a non-iso image of the distribution.

Making a bootable installation disk	
dd if=/path/to/<image_name> of=/dev/fd0	on a linux box
rawrite.exe	under Windows (not NT)

For RedHat distributions the installation images are in the images directory. The basic image is boot.img. Other images are more specialised like bootnet.img or pcmcia.img.

In a Suse distribution the floppy image is in the disks directory and the image is called bootdisk.

3. Network Installation

For a RedHat installation this is only a specialised floppy installation. Make a bootable floppy using the bootnet.img image:

dd /mnt/cdrom/images/bootnet.img of=/dev/fd0

The first part of the installation is text based and will allow you to set up the keyboard and the network parameters needed. The rest of the installation can be done via FTP, NFS or HTTP. Originally protocols that allowed a full mount (NFS) would also allow the install to be done in graphical mode, while file retrieval protocols (FTP HTTP) would only allow text mode. With most modern distributions this is no longer the case.

Also notice that most modern distributions offer network installations directly from the CD (e.g Mandrake disk 2 will start a network type installation or Fedora Core can take the parameter askmethod at boot time).

4. Rescue disk

If a Linux system is corrupt it is possible to boot the computer using a rescue disk. This is a small version of Linux that will mount a minimal virtual filesystem into memory.

The Linux operating system runs entirely in RAM. The aim is to access the root filesystem on the PC hard drive. Most rescue disks can determine this automatically. Assuming the root filesystem was found on the first logical partition of the computer's first IDE disk (/dev/hda5), the rescue disk script can then mount this resource on a subdirectory of the filesystem in RAM, say /mnt/system.

Changing perspectives

In this situation we have two root filesystems as depicted below. To use the root filesystem on the hard drive as our top directory we need to change our perspective (change root). The chroot tool does just that:

chroot /mnt/sysimage

Rescue mode
RAM kernel initrd root filesystem in RAM root filesystem on PC hard drive

Getting started

Old Method:

Make a bootable floppy using the boot.img image file: dd if=boot.img of=/dev/fd0

Copy the rescue.img image file to a second floppy: dd if=rescue.img of=/dev/fd0

Boot the system using with the boot.img diskette

At the LILO prompt type "linux rescue". You should see something like

Insert root file system disk:

Insert the rescue.img diskette and press enter

The boot process will continue until you get a shell prompt

You may still need to determine where the root filesystem is on the hard drive (not covered)

New Method:

1. Insert the Linux installation disk (Suse, RedHat, Mandrake ...)

2. At the prompt type “linux rescue”

3. Follow the instructions.

4. The instuction should say where the root filesystem is mounted

5. If the root filesystem is mounted on /mnt/sysimage then enter the following command

5. Partitioning Schemes

To access resources on a hard drive the operating system uses a mechanism called 'mounting'. For UNIX type operating systems this involves attaching a disk to any directory which is then called a mount point.

The figure below shows a possible partitioning scheme. Here many resources (not only local disks and partitions, but possibly network shares, CD-ROMs, etc) are attached on various mount points

To the user the file system layout is simply a tree of directories and subdirectories.

Forming a tree-like filesystem structure

The root of the tree structure is called root and is represented by a forward slash “/”. The root mount point is also the first directory on which the operating system will attach a disk or resource, also called the root device.

Once the root is mounted the directories and subdirectories present on the root device can be used as further mount points for other devices, forming a succession of directories ordered like a tree.

The process is made possible as follows:

1. The bootloader will load a kernel telling it where the root device is (also see "Booting Linux" LPI 102)

2. The other directories are mounted following instructions from the /etc/fstab file (see p.33)

Mount points on the file system

Creating the Disk Layout

When installing Linux one has to create a partition scheme. This is a particular stage of the installation process and is done most often with a GUI tool such as Yast or DiskDruid. These tools allow one to do three things:

create partitions of a given size

select the filesystem type (see p.42)

assign a mount point for each partition.

Some installations have an 'expert mode' where it is possible to use fdisk (see p.29) to create the partitions only.

A minimal partition scheme involves one root device and another partition for swapping. There are no rules when creating a disk layout but one generally takes into account the function of the computer (desktop, mail server, etc).

The SWAP partition

When creating a partition scheme one also has to make decisions about the amount of swap space needed. Once again, there are no rules. The amount of swap space needed depends of the type of applications that will run on the PC (desktop, server, 3D rendering, etc. ). However as a rule of thumb, for a 2.4 kernel with an average amount of RAM (e.g less than 256MB) one will generally create a swap space twice as large as the amount of RAM. With older 2.2 kernels one would create a swap partition of the same size as the amount of RAM.

Swapping is generally done using a partition. In the partition table the hexadecimal value for a swap partition is 82.

NOTICE
Unlike partitions used for storing data a swap partition is never mounted. One also doesn't assign a mount point for such partitions. To create a SWAP space during the installation on simply selects the 'filesystem type' labelled 'SWAP'. Once the system is running information about the SWAP partitions is available in /proc/swaps

One can also create SWAP space areas using files rather than partitions (see LPI 201). This is often used for emergencies once a system is running and not during the installation.

6. Easy Dual Booting

(This section is not for exam purposes and can be left out completely).

If Windows9x/2k is already installed on the system the installation setup will automatically configure LILO for dual booting.

Pre-installation:

Before altering the system you should run a defragmentation program over the whole disk. This will make sure that all the blocks used by the Windows operating system are rearranged at the beginning of the disk.

Next, using PartitionMagic or fips, partition the C:\ drive in two. The Windows programs are located at the beginning of the hard disk in the first partition. The second partition must be large enough to hold a Linux installation.

Notice: The average amount of space needed for a Linux distribution is 4GB.

Starting the installation from DOS:

For non-NT systems restart your computer in DOS command mode. If you are installing RedHat then you can run E:\DOSUTILS\AUTOBOOT.BAT. This will start the installation program. Similarly if you are installing Suse you can run E:\setup.exe under DOS.

The hard drive from a Windows' perspective:

When running Windows the OS will only see the FAT and NTFS filesystems. The rest of the disk where Linux is installed will be inaccessible.

The hard drive from a Linux point of view:

When running Linux the Windows partition should be called /dev/hda1 (since it's the first partition on the first physical disk). By default this partition is not mounted. You can make a directory /dos or /mnt/dos and mount this partition. The disk partition corresponding to C:\ is then accessible.

7. Exercises and Summary

Review Questions (answers p.150)

Yes or No

1. The rawrite tool runs under Linux and is used to copy an image file onto a floppy disk	_____

2. When devising a new partition scheme on an empty disk any disk partition can be chosen as the root

device	_____

Glossary

Term	Description
virtual filesystem	a filesystem is a data structure that allows data on a disk to be organised and accessed by the user. However to the user data is simply located in a series of directories and subdirectories. These directories form a tree structure with a top directory called the root and noted " / ". This structure is also called the 'virtual filesystem' because one doesn't need to know anything about the disk layout or partitioning scheme in order to use it. This is different to the situation when using a DOS based system; there if the disk has four partitions all the users will need to know that data can be in either C:\, D:\, E:\ or F:\ and, in this example, that the first CD-ROM is the G:\ device
mount point	a directory where a partition is attached in order to make the device available to the system
partitioning scheme	action performed during the installation to fix the number of partitions and mount points in order to create a standard 'virtual filesystem' on which software is installed. The standard which decides where software components are installed or where user home directories are kept is called the filesystem hierarchy standard (FHS) and should influence our choices when installing Linux (e.g most software is installed in the /usr directory, therefore always make sure that this directory is on a fairly large partition, at least 2 GB in most cases)
rescue mode	action of running a Linux operating system entirely in RAM together with a small root filesystem containing enough tools to access the hard drive. This is generally started with an installation CD
root (/)	the top directory where a first partition is attached. Either all the directories and subdirectories needed can be found on this partition or certain subdirectories of root can be used as mount points to attach further partitions (this depends on the partition scheme chosen during the installation!)

Commands

Command	Description
chroot	change into a directory and consider that directory as the root (/). By default chroot tries to run the Bash shell /bin/bash, but it is possible to specify any other command (see 'chrooted servers' in LPI 202)
dd	tool used to copy files as well as portions of a device (e.g hard drive, CD-ROM or floppy). An installation CD contains files called 'image files' which are copies of installation or driver disks that can be copied back onto a floppy
fips.exe	a utility found on most Linux distribution CDs that is used to resize a FAT partition in order to make space for a dual boot Windows/Linux system
rawrite	a DOS equivalent of dd

Exercises

1. Do a local CD installation. The following points outline a suggested strategy. The OPTIONAL points should be attempted only by advanced users familiar with package management and the vi editor.

(i) Installation Type: choose “Custom”

(ii) Disk Partitioning Setup: Partition the disk manually with Disk Druid:

This is a suggestion for a partitioning scheme using about 3GB of hard disk space. If you have more space available then make /usr larger and consider installing more packages than those suggested in step (iv)

IMPORTANT: Leave a free partition of at least 100MB. We will need this later!!

/boot	20M

/	250M

/usr	2300M

/home	50M

/tmp	100M

/var	150M

SWAP	128M Notice that SWAP is a filesystem type and that no mount point is defined – see p.6

(iii) (OPTIONAL) Install LILO on /dev/hda2 or not at all. In all cases do not use the suggested /dev/hda, which is the MBR.

We deliberately don't want the installation to boot properly. The bootloader will be fixed in step 2(i)	in rescue mode.

(iv) Packages to install: (the names may vary from one distribution to another)

“X Window System” + “GNOME desktop environment” OR “KDE desktop environment”

“Editors”

“Graphical Internet”

“Software Development” [This is important, we will need this to compile packages later]

(v) Don’t create a bootable floppy

2. (OPTIONAL) Rescue the system:

(i) Reboot with the installation CDROM. At the prompt type:

linux rescue

(ii) Read all the instructions until you get to a prompt. Use the chroot command as suggested.

(iii) You first need to install the lilo package. Edit /etc/lilo.conf (use vi). You should have

boot=/dev/fd0

prompt

linear

timeout=50

image=/boot/vmlinuz-<kernel-version>

label=linux

read-only

root=/dev/<root-partition>

(v) Run /sbin/lilo. If an error occurs you may have to replace linear by lba32 depending on your disk.

Hardware Configuration

Prerequisites

None

Goals

Understand hardware resource allocation (IRQs, I/O ports and DMA)

Overview hardware devices such as expansion cards, USB and SCSI devices	Detection of network interfaces and printers (no configuration)

Understand basic configuration steps for modems and sound cards

Contents

Hardware Configuration	10

1. Resource Allocation	11

2. PC Expansion Cards	12

3. USB Support	13

4. SCSI Devices	14

5. Network cards	15

6. Setting up modems	16

7. Printer Configuration	21

8. Sound Cards	22

9. Exercises and Summary	24

1. Resource Allocation

To allow peripherals and devices on the PC to communicate directly with system resources, in particular the CPU, the system allocates resources such as lines and channels for each device. These resources are Interrupt Request Lines (IRQ), Input/Output addresses and Direct Memory Access channels (DMA).

IRQs: The Interrupt Request Lines allow devices to request CPU time. The CPU will stop its current activity and process the instructions sent by the device. IRQs range from 0 to 15.

I/O address: These represent specific addresses in the system’s memory map. The CPU will then communicate with the device by reading and writing to memory at the specified address.

DMA: Certain devices can access the system’s memory through a DMA channel, allowing them to write and process data without accessing the CPU. This can enhance performance.

● Listing Allocated Resources

The kernel keeps information related to allocated resources in the /proc directory. The relevant files are:

/proc/dma
/proc/interrupts
/proc/ioports
/proc/pci

Allocated resources can also be listed using tools such as lspci and dmesg:

lspci: lists chipset information of all attached PCI components. Lists I/O and IRQ settings with the -v flag . Also notice the -b (BUS centric) option which shows allocations assigned by the BIOS rather than the kernel.

dmesg. Continuously displays kernel messages. It also displays the kernel messages logged at boot time during the “ kernel” stage . At this stage the kernel scans all the hardware on the system and can automatically allocate modules (drivers) for given chipsets. These messages are also available in /var/log/dmesg.

● Typical Resources

Device	I/O port	IRQ
/dev/ttyS0	0x03f8	4
/dev/ttyS1	0x02f8	3
/dev/lp0	0x378	7
/dev/lp1	0x278	5
soundcard	0x220	

Manual Resourse Allocation

NOTICE: This is a very common example, however since kernel modules are only discussed in LPI 102 some may find it difficult. You may skip this example and go to section 2

Example: configuring two ethernet cards

1. For statically compiled modules, parameters can be passed to the kernel at boot time. A typical example is when two ethernet cards are present and only the first one is detected. The following line tells the kernel that:

- there is an ethernet card using IRQ 10 and I/O 0x300

- there is another ethernet card using IRQ 9 and I/O 0x340

ether=10,0x300,eth0	ether=9,0x340,eth1

You type this line at the LILO/GRUB ‘boot:’ prompt, or else, as with the RAM settings before, edit

/etc/lilo.conf (use an append= statement) or /etc/grub.conf.

Notice that the ether= statement is a generic kernel command similar to root=, mem= or init=.

Also notice that you need not specify any information about the ethernet card (Intel, Netgear ...)

2. For dynamically compiled modules, IRQ and I/O address settings can be defined using /etc/modules.conf (or /etc/conf.modules). Assuming that in the above example both cards where using the e100.o kernel module, then /etc/modules.conf would contain the following:

alias eth0 e100

alias eth1 e100

options eth0 io=0x300 irq=10

options eth1 io=0x340 irq=9

2. PC Expansion Cards

ISA and PCI are the most common types of expansion cards. With the latest 2.4 kernel there is very little to be done in order to configure these. In the case of ISA buses however, and only with earlier kernels, it was necessary to scan the ISA bus in order to detect existing expansion cards (sound, ethernet, etc).

The isapnptools package provided the pnpdump tool which scanned the ISA bus for 'Plug and Play' (pnp) devices. The output would contain the chipset of the card together with I/O port, DMA and IRQ settings. This output would be redirected to /etc/isapnp.conf where changes could be made if needed. At boot time the isapnp tool would read isapnp.conf and would configure these ISA PnP devices.

Since kernel 2.4 PnP initialisation is supported through a kernel module called isapnp.o

3. USB Support

The Universal Serial Bus (USB) is a communication architecture designed to connect devices to a PC. These devices are divided into four classes:

Display Devices

Communication Devices

Audio Devices

Mass Storage Devices

Human Interface Devices (HID)

The devices are plugged into a USB port which is driven by a USB controller. Support for USB controllers is present in the Linux kernel since version 2.2.7 ( The Linux USB sub-system HOWTO)

Host Controlers

There are 3 types of USB host controllers:

Host Controler Kernel Module
OHCI (Compaq)	usb-ohci.o
UHCI (Intel)	usb-uhci.o
EHCI (USB v 2.0)	ehci-hdc.o

Once a USB device is plugged into a PC we can list the devices withlsusb:

lsusb
Bus 001 Device 001: ID 0000:0000
Bus 001 Device 002: ID 04a9:1055 Canon, Inc.

Hotplugging

Hotplug is a mechanism used to keep the state of the operating system updated when pluggable hardware devices are added or removed. In most cases the kernel signals an event by passing parameters to the script /sbin/hotplug.

This hotplug script runs all the scripts in /etc/hotplug.d (the default is default.hotplug) which in turn starts the appropriate agent listed in /etc/hotplug. The names of the agents correspond to different attachment types such as ieee1394, net, pci, scsi and usb.

The following log describes what happens when a USB camera is initialised:

Stage 1: USB kernel modules identify USB event and vendor/product ID:
13:26:19 kernel: hub.c: new USB device 00:07.2-1, assigned address 5
13:26:19 kernel: usb.c: USB device 5 (vend/prod 0x4a9/0x3058) is not claimed by any active driver.

Stage 2:The event arguments are passed to default.hotplug
13:26:19 default.hotplug[10507]: arguments (usb) env (DEVFS=/proc/bus/usb OLDPWD=/ PATH=/bin:/sbin:/usr/sbin:/usr/bin ACTION=add PWD=/etc/hotplug HOME=/ SHLVL=2 DEVICE=/proc/bus/usb/001/005 PRODUCT=4a9/3058/1 TYPE=255/255/255 DEBUG=yes _=/bin/env)

Stage 3: The usb.agent associates the product to a usbcam (using usb.usermap)
13:26:19 default.hotplug[10507]: invoke /etc/hotplug/usb.agent ()
13:26:23 usb.agent[10507]: Setup usbcam for USB product 4a9/3058/1
13:26:23 usb.agent[10507]: Module setup usbcam for USB product 4a9/3058/1
13:26:38 devlabel: devlabel service started/restarted

From this we can see that Step 1 involves the kernel modules and Step 2-3 involve the hotplug mechanism. One can also see that the correct USB map must be available in order to fully initialise the device.

The usbmgr tool

On Debian systems an alternative to hotplug is provided with the usbmgr package. The main files are:

/usr/sbin/usbmgr	The daemon that listens for USB related events

/usr/sbin/dump_usbdev	Tool to list USB devices (similar to lsusb)

/etc/usbmgr/usbmgr.conf	Configuration file containing vendor/product IDs

4. SCSI Devices

Types of SCSI devices

There are two types of SCSI interfaces:

- an 8-bit interface with a bus that supports 8 devices, this includes the controller, so there is only space for 7 block devices (tapes, disks, etc)

- a 16-bit interface (WIDE) with a bus that supports 16 devices including the controller, so there can only be 15 block devices.

SCSI devices are uniquely identified using a set of 3 numbers called the SCSI ID:

a. the SCSI channel

b. the device ID number

c. the logical unit number LUN

The SCSI Channel

Each SCSI adapter supports one data channel on which to attach SCSI devices (disc, CDROM, etc)

These channels are numbered from 0 onwards.

Device ID number

Each device is assigned a unique ID number that can be set using jumpers on the disk. The IDs range from 0 to 7 for 8-bit controllers and from 0 to 15 for 16-bit controllers.

Logical Units

The Logical Unit Number (LUN) is used to differentiate between devices within a SCSI target number. This is used, for example, to indicate a particular partition within a disk drive or a particular tape drive within a multi-drive tape robot. It is not seen so often these days as host adapters are now less costly and can accommodate more targets per bus.

Hardware Detection

All detected devices are listed in the /proc/scsi/scsi file. The example below is from the SCSI-2.4-HOWTO

/proc/scsi/scsi
Attached devices:
Host: scsi0 Channel: 00 Id: 02 Lun: 00
Vendor: PIONEER Model: DVD-ROM DVD-303 Rev: 1.10
Type: CD-ROM ANSI SCSI revision: 02
Host: scsi1 Channel: 00 Id: 00 Lun: 00
Vendor: IBM Model: DNES-309170W Rev: SA30
Type: Direct-Access ANSI SCSI revision: 03

The scsi_info tool uses the information in /proc/scsi/scsi to printout the SCSI_ID and the model of a specified device. From the file above scsi_info would produce the following output:

scsi_info /dev/sda
SCSI_ID="0,0,0"
MODEL="IBM DNES-309170W"
FW_REV="SA30"

Booting from SCSI disks

The system will boot from the device with SCSI ID 0 by default. This can be changed in the SCSI BIOS which can be configured at boot time.

If the PC has a mixture of SCSI and IDE disks, then the boot order must be selected in the systems BIOS first.

5. Network cards

The network interface card (NIC) must be supported by the kernel. You can get information about your current card using either of the following:

dmesg, lspci, scanpci, /proc/interrupts, /sbin/lsmod.or /etc/modules.conf:

dmesg
► Linux Tulip driver cersion 0.9.14 (February 20, 2001)
PCI: Enabled device 00:0f.0 (0004 ->0007)
PCI: Found IRQ 10 for device 00:0f.0
eth0: Lite-On 82cl68 PNIC rev 32 at 0xf800, 00:0A:CC:D3:6E:0F,
IRQ 10
eth0: MII transceiver #1 config 3000 status 7829 advertising

cat /proc/interrupts

►	0: 8729602 XT-PIC timer

1: 4 XT-PIC keyboard

2: 0 XT-PIC cascade

7: 0 XT-PIC parport0

8: 1 XT-PIC rtc

10: 622417 XT-PIC eth0

11: 0 XT-PIC usb-uhci

14: 143040 XT-PIC ide0

15: 180 XT-PIC ide1

/sbin/lsmod

►	Module Size Used by

tulip 37360 1 (autoclean)

From the examples above we see that the Ethernet card’s chipset is Tulip, the i/o address is 0xf800 and the IRQ is 10. This information can be used either if the wrong module is being used or if the resources (i/o or IRQ) are conflicting.

This information can either be used to insert a module with a different i/o address (using the modprobe or insmod utilities) or can be saved in /etc/modules.conf (this will save the settings for the next bootup).

6. Setting up modems

We first need to detect the modem. If the modem is an external modem all one needs to consider is the serial port it is using. However when dealing with a built-in PCI modem we need information about the I/O port and interrupt used by the device in order to determine which serial device should be configured.

● The Modem device

If we have an external modem we can go straight to the next section 'The serial port'.

A PCI modems device can be detected with lspci. (the listing below is from PCI-Modem micro-HOWTO):

lspci -v
----- snip -----
► 00:0c.0 Serial controller:US Robotics/3Com 56K FaxModem Model 5610 (rev 01) (prog-if 02 [16550])
Subsystem: US Robotics/3Com USR 56k Internal FAX Modem (Model 2977)
Flags: medium devsel, IRQ 11
I/O ports at e800 [size=8]
Capabilities: <available only to root> ------ snip ----

Notice that the I/O port is 0xe800 and the IRQ is 11

We can now use this information and assign these resources to a serial port device.

● The serial port

The modem uses a serial interface for communications. Information is sent through the telephone line as a sequence of bits (serial) over two wires (in and out). Incoming sequential data is translated into parallel data for the PC bus and vice versa for bits of data leaving the computer. The translation is done by a UART chip located on the serial port of the motherboard or inside an internal (PCI) modem.

To see which serial ports were detected at boot time on the system, we do the following:

dmesg | grep ttyS

► /dev/ttyS0, UART: 16550A, Port: 0x03f8, IRQ: 4
/dev/ttyS1, UART: 16550A, Port: 0x02f8, IRQ: 3

So far, these are preconfigured serial ports with I/O ports and IRQs generally used by a hardware serial port.

NOTICE
When configuring an external modem one only has to consider serial devices with IRQ 3 or IRQ 4. The I/O ports reported above are also standard addresses used by hardware serial ports

The following table shows the equivalence between DOS COM ports and Linux serial devices.

Serial port equivalence DOS-Linux

DOS	Linux
COM1	/dev/ttyS0
COM2	/dev/ttyS1
COM3	/dev/ttyS2

One can also use setserial to scan the serial devices. With the -g option this utility will tell you which serial devices are in use:

setserial -g /dev/ttyS[01]

► /dev/ttyS0, UART: 16550A, Port: 0x03f8, IRQ: 4

/dev/ttyS1, UART: 16550A, Port: 0x02f8, IRQ: 3

Now if we have a PCI modem as the one detected using lspci on p.16 we need to remember the I/O port and IRQ setting used:

Hardware setting for the PCI modem on p.16
I/Oport	0xe800
IRQ	11

This time we will use setserial to assign these values to a serial device (other than the hardware serial devices) as follows:

setserial /dev/ttyS4 port 0xe800 irq 11 autoconfig

The autoconfig option automatically sets the correct UART. This command can be saved in a shell script called serial.rc and will configure the serial port every time we boot.

A symbolic link called /dev/modem pointing to the used serial port is often used to reference the modem.

Manually linking the modem device

ln -s /dev/ttyS1 /dev/modem

The setserial tool is also used to set the speed of the serial port.

setserial speed option	Description
spd_hi	use 56kb instead of 38.4kb
spd_vhi	use 115kb instead of 38.4kb
spd_shi	use 230kb instead of 38.4kb
spd_warp	use 460kb instead of 38.4kb
spd_cust	use the custom divisor to set the speed at 38.4kb (baud rate = baud_base / custom_divisor)
spd_normal	use 38.4kb when a baud rate of 38.4kb is selected

For example setting the speed for the serial port /dev/ttyS4 to 115kb is done as follows:

setserial /dev/ttyS4 spd_vhi

● Dialup Configuration

The wvdial commandline tool has a setup script called wvdialconf which will scan the system for modems (all serial and USB ports are scanned automatically). Once the script has run a skeleton configuration file is generated:

Sample /etc/wvdial.conf file:

[Dialer Defaults]

Modem = /dev/ttyS1

Baud = 115200

Init1 = ATZ

Init2 = ATQ0 V1 E1 S0=0 &C1 &D2 S11=55 +FCLASS=0

; Phone = <Target Phone Number>

; Username = <Your Login Name>

; Password = <Your Password>

A quick way to get started is to replace Defaults with the name of your provider say WorldISP, fill in the Usernam/Password entries and type the following:

wvdial WorldISP

One can also use minicom to configure a connection. This tools is first configured with the -s switch:

minicom -s [configuration] Filenames and paths File transfer protocols Serial port setup Modem and dialing Screen and keyboard Save setup as dfl Save setup as.. Exit Exit from Minicom

All the work done on serial ports will be useful in the 'Serial port setup' section, whereas dialling information (given by the ISP) can be entered by selecting the menu 'Modem and dialing'

Once the modem is set up and is capable of dialling the outside world then it is possible to establish a serial connection to a remote host. To get a fully networked connection (i.e assign an IP address to a network interface) we still need to start the pppd which will create a ppp0 network interface and uses the point to point protocol PPP to enable TCP/IP networking. With tools like wvdial this is done automatically when needed.

● WinModems

If all the above configurations fails then it likely that you have a modem that may only work with some added drivers. Such modems are called winmodems (see the winmodem HOWTO for some colourful definitions!).

A winmodem that can be made to work under Linux is also called a linmodem. (see the linmodem HOWTO for more details)

ISDN

ISDN is a digital version of the “Plain Old Telephone Service” (POTS). It functions in a similar way, but instead of allowing a single direct analogue path, offers a number of 64KBit/S traffic or bearer channels and a low bandwidth data channel. ISDN2, the basic service offered in many countries, is a so called 2B+D service as it offers two bearer channels and a data channel.

There are a number of ways of using ISDN with a Linux machine. The simplest is to employ an external ISDN device that does the dialing, authentication and session for you, presenting the connection over an Ethernet network.

If the Linux machine is to be directly interfaced to the ISDN connection, a device called a Terminal Adapter (TA) will be required. The details of the various different interfaces to TAs are outside the scope of this course, but fall mainly into the following camps.

Modem Style AT command Interface

With serial connected TAs and some USB devices, the Linux machine is presented with an AT command interface exactly as if the TA were a modem. The TA can therefore be set up as if it were a modem. This has the advantage of being simple to do, but is less efficient than some other methods as it treats the data path as if it were a modem as well. Modems require that some characters are escaped as they have an active effect. ISDN has no such restriction and can pass any character.

PCI/ISA/PCCARD ISDN adapter cards and isdn4linux

A far more efficient way of using your ISDN line is to use an adapter card connected directly to a machine bus. The isdn4linux project seeks to encapsulate a lot of the details of making a connection over ISDN and present the finished connection as just another network interface. The package isdn4k-utils contains all the necessary software. Under Red Hat related Linux distributions the tool “system-config-network” will set this all up.

ADSL

Asynchronous Digital Subscriber Line (ADSL) has largely replaced ISDN and private leased lines as the mass market higher bandwidth Internet connection method of choice. As with ISDN the Linux user has a number of strategy choices. The simplest, again as with ISDN, is to employ any of a number of different stand alone ADSL Router devices. These present the outside link via an Ethernet router. No special considerations need be taken on the Linux machine. The ADSL router is treated as an ordinary router. Many of these ADSL router devices are actually themselves embedded Linux machines. If the Linux user requires a closer connection to the ADSL service, they will probably need to acquire equipment and an ISP account capable of Point-to-Point Protocol over Ethernet (PPPoE). There are ADSL projects based around particular chipsets, but they have their own specific requirements and configuration methods.

PPPoE

ADSL is not a single protocol but rather a basket of related and interconnected protocols topped off with Point-to-Point Protocol (PPP). If the equipment and the ISP account are compliant, the Linux user can employ PPPoE to form the external connection. The Linux machine would initiate a PPPoE session and aim it at the MAC address of the ADSL equipment. The ADSL equipment would set up the layers beneath the PPP session and pass the PPP frames across those layers. The package “pppoe” contains all necessary software and setup information.

7. Printer Configuration

Printing is covered in depth in LPI 102. From a hardware perspective, the printers are detected at boot time automatically and can be seen in the dmesg output.

Linux printing happens in two stages. First the raw data is filtered into a postscript format, then the printing itself is handled by the ghostscript, or gs utility.

Using printtool	(not examined)

This utility creates an entry in /etc/printcap. The main features which need to be specified are the location of the input_filter=if, the spool_directory=sd and the printer_device=lp.

If the printtool fails to detect which parallel port corresponds to the printer device you can use the dmesg utility to recall the kernel's initial parallel port scan.

Here is an example of a system with a local printer plugged into the first parallel port /dev/lp0

Parallel port scan at the end of dmesg
parport0: PC-style at 0x378 (0x778) [SPP,ECP,ECPEPP,ECPPS2] parport0: detected irq 7; use procfs to enable interrupt-driven operation. parport_probe: succeeded parport0: Printer, HEWLETT-PACKARD DESKJET 610C lp0: using parport0 (polling)

Sample /etc/printcap file
# This file can be edited with the printtool in the control-panel. ##PRINTTOOL3## LOCAL cdj550 300x300 a4 {} DeskJet550 3 {} lp:\ :sd=/var/spool/lpd/lp:\ :mx#0:\ :sh:\ :lp=/dev/lp0:\ :if=/var/spool/lpd/lp/filter:

Figure 7: The gtk-based printtool GUI

Using cups

Cups is a newer administration and configuration tool for printers. It's main configuration files are stored in

/etc/cups. The printing process is the same except that cups uses its own filters situated in /usr/lib/cups.

The configuration tool for CUPS is a Web based GUI running on port 631.

 When using cups lpd is replaced by the cupsd daemon.

NOTICE
A local printer is physically detected at boot time for both USB and parallel connections. Information on the boot process is displayed at any time with dmesg

8. Sound Cards

There are two sound support projects for Linux, namely the open sound system (OSS) and the advanced Linux sound architecture (ALSA). In fact the OSS is a commercial project which supports sound drivers on other UNIX platforms. The original modified OSS drivers where introduced as part of the Linux 2.0 kernel.

The ALSA project is more recent and has only been integrated into the Linux 2.6 kernel. For kernels older than 2.6, using ALSA drivers often means recompiling the kernel except for some Linux distributions such as Suse which adopted ALSA at an early stage.

In most cases the card is configured when the system is installed. Graphical sound configuration tools are also included with all main Linux distributions.

Detecting the sound card

As usual we will use dmesg to see if the kernel has detected the sound card as follows:

dmesg | grep -i audio NeoMagic 256AV/256ZX audio driver, version 1.1p Initialized NeoMagic 256ZX audio in PCI native mode

NOTICE
The command above may return nothing, in which case you must search the output of dmesg again and try to determine which device corresponds to the sound card

Using the sndconfig tool (LPI101 objective p.152)

The above sound card would be fully configured if we could find the correct kernel module using the information found with dmesg. In the OSS framework this kernel module is then associated to a device name used by applications called sound-slot-0 (for the first sound device).

This is what a sound configuration tool will do automatically for us. We choose (since it is an LPI101 objective) to discuss sndconfig.

This is a RedHat tool that configures audio devices using the OSS modules. You may need to install sndconfig as it is no longer installed on most Linux distributions. Then one simply types:

sndconfig

A graphical menu will be started with a message suggesting it will now probe for audio devices on you system. Select 'OK'.

On our system the following hardware was detected:

Neomagic Corporation | NM2360 [MagicMedia 256ZX Audio]

If no device is detected you will be presented with a list of manufacturers and card models supported by OSS from which to choose. If this happens, you may want to check the output of lspci again and also the following site with supported models: http://www.opensound.com/osshw.html

Once a model has been chosen sndconfig will attempt to load the associated kernel module and play a sample (surprise!) sound. If this worked then the /etc/modules.conf (covered in LPI 102) is automatically modified for us. To illustrate how our particular card has been configured here is the sound module entry:

/etc/modules.conf (entry for sound card used in this section)
alias sound-slot-0 nm256_audio

9. Exercises and Summary

Review Questions (answers p.150)

Yes or No

1. The root partition of a Linux system must always be on an IDE disk	__________

2. A Linux system can support any USB device as long as the kernel has

been compiled with USB support	__________

Glossary

Term	Definition
DMA	Direct Memory Access allows certain hardware components to access memory to perform read-writes without having to interrupt the CPU
I/O address	a predefined memory range used by hardware devices and the CPU to perform read and write operations
IRQ	signal sent to the CPU by a device in order to interrupt the current process and get it to do something else
resource allocation	collection of DMA, i/o port and IRQ settings allocated to a hardware device
SCSI	interface used to transfer data between a device and the computer bus. For example the device can be a hard drive, a tape drive, a CD-ROM, a CD writer or a scanner
USB	Universal Serial Bus is a standard allowing external hardware devices to be attached to a computer without having to reboot. The design consists of a host controller to which is attached an initial hub device. This hub can then accommodate USB devices or more hub devices allowing to attach up to 127 devices (including hubs) to a single host controller

Resources

The Winmodems-and-Linux HOWTO

The Serial HOWTO

The Modem HOWTO

The Linux USB sub-system (http://www.linux-usb.org/)

SCSI terminology (http://www.scsita.org/terms/scsiterms.html)

The Linux 2.4 SCSI subsystem HOWTO

The Ethernet HOWTO

The Printing HOWTO

The Sound HOWTO

The isdn4linux project (http://www.isdn4linux.de/)

The Roaring Penguin PPPoE project (http://www.roaringpenguin.com/penguin/open_source_rp-pppoe.php)

Files

File	Description
/etc/isapnp.conf	a configuration file for isapnp - see isapnp.conf(5)
/proc/dma	list of currently used DMA channels
/proc/interrupts	list of currently used interrupts
/proc/ioports	list of currently used i/o ports
/proc/pci	list current information about the PCI bus
/etc/hotplug/usb.usermap	list of recognised USB devices
/var/log/dmesg	log file for current and boot time kernel messages
/proc/scsi/scsi	information about all SCSI devices – see scsi_info(8)

Commands

Command	Description
dmesg	print kernel message since boot time
hotplug	program used by the kernel to handle hardware related events - see hotplug(8)
isapnp	tool used to initialise ISA cards prior to kernel 2.4 – see isapnp(8)
lspci	list all PCI devices – see lspci(8)
lsusb	list all USB devices – see lsusb(8)
pnpdump	pnpdump(8) – dump ISA Plug-And-Play devices resource information
scsi_info	scsi_info(8) – SCSI device description tool
setserial	setserial(8) - get/set Linux serial port information
usbmgr	user space daemion which loads or unloads USB modules. It is an alternative to hotplug and generally used on Debian based systems
usb.agent	a hotplug agent which handles USB related events
usbmodules	usbmodules(8) – lists driver modules that may be able to manage interfaces on currently plugged in USB devices. usbmodules may be used by /sbin/hotplug or one of its agents (normally /etc/hotplug/usb.agent) when USB devices are "hot plugged" into the system
wvdial	a PPP dialer – see wvdial(1)

Exercises

1.	Use the dmesg command to view the /var/log/dmesg file. Search for keywords such as USB, tty or ETH0.

- What are the names of the USB controllers used?

- What are the IRQs for the first two serial ports?

2.	Investigate the contents of the following files:

/proc/ioports
/proc/interrupts

/proc/pci

/proc/dma

3.	The PCI bus:

- Investigate the output of lspci -v and scanpci –v. What type of ethernet card is

present?

- Verify that there are as many ‘bus ’ entries listed with lspci and /proc/pci.

4.	USB tools:

- Use lsmod and lsusb to determine which host controller is used on your

system, UHCI, OHCI or EHCI (for USB v 2.0).

- Use usbmodules to list the kernel module which can handle the plugged in interface.

5.	SCSI devices

- Given the following contents of the file /proc/scsi/scsi deduce the output of the	command scsi_info (see p.15):

Attached devices:

Host: scsi0 Channel: 00 Id: 00 Lun: 00

Vendor: PHILIPS Model: CDRW48A Rev: P1.3

Type: CD-ROM ANSI SCSI revision: 02

Managing Devices

Prerequisites

Experience with the Linux installation process (also see the section Installation on p.1)

Goals

Understand the difference between a primary, an extended and a logical partition

Use partitioning tools when appropriate ( before or after an installation )

Install and customise the boot loaders LILO and GRUB

Understand mount points and the role of the /etc/fstab file

Contents

Managing Devices	27

1. Disks and Partitions	28

2. Partitioning Tools:	30

3. Bootloaders	31

4. Managed devices	33

5. Quotas	35

6. Exercises and Summary	36

1. Disks and Partitions

Physical disks:

On a running Linux system, disks are represented by entries in the /dev directory. The kernel communicates with devices using a unique major/minor pair combination. All major numbers are listed in /proc/devices. For example the first IDE controller‘s major number is 3:

Block devices:

1 ramdisk

2 fd

3 ide0

Hard disk descriptors in /dev begin with hd (IDE) or sd (SCSI), a SCSI tape would be st, and so on. Since a system can have more than one block device, an additional letter is added to the descriptor to indicate which device is considered.

Table 1	Physical block devices
hda	Primary Master
hdb	Primary Slave
hdc	Secondary Master
hdd	Secondary Slave
sda	First SCSI disk
sdb	Second SCSI disk

NB Inserting a new SCSI hard drive with a target number between two existing drives will bump up the device letter of the higher numbered drive. This can cause chaos within a disk system.

Disk Partitions:

Disks can further be partitioned. To keep track of the partitions a number is added at the end of each physical device.

Table 2	Partitions
hda1	First partition on first hard disk
hda2	Second partition on first hard disk
sdc3	Third partition on third SCSI disk

IDE type disks allow 4 primary partitions, one of which can be extended. The extended partition can further be divided into logical partitions. There can be a maximum of 64 partitions on an IDE disk and 16 on a SCSI disk.

Example 1: The primary partitions (1,2,3,4) and (1,2,5,6,7,8)

Typical output of fdisk -l

Device Boot Start End Blocks Id System /dev/hda1 * 1 748 6297448+ b Win95 FAT32 /dev/hda2 785 788 32130 83 Linux /dev/hda3 789 2432 13205430 5 Extended /dev/hda5 789 1235 3590496 83 Linux /dev/hda6 1236 1618 3076416 83 Linux /dev/hda7 1619 1720 819283+ 83 Linux /dev/hda8 1721 1784 514048+ 83 Linux /dev/hda9 1785 1835 409626 83 Linux /dev/hda10 1836 1874 313236 83 Linux /dev/hda11 1875 1883 72261 82 Linux swap

On this system the main feature to notice is that there are 3 primary partitions. The third partition is extended (/dev/hda3) and holds 8 logical partitions. The primary partition /dev/hda3 is not used. In fact /dev/hda3 acts as a 'container' and a filesystem exists only on the enclosed logical partitions.

NOTICE
Make sure to distinguish between primary, extended and logical partitions. Also make sure you understand the naming convention for the IDE disks and controllers.

2. Partitioning Tools:

1. Before installation:	(not for exam purpose)

PartitionMagic

fips

Notice that fips only handles fat16 and fat32. On the other hand, PartitionMagic is much more versatile and can handle most common UNIX formats as well.

No partitioning is needed if for example C:\ and D:\ exist and the D:\ drive is empty.

Partitioning before installation:

2. During installation:	(not for exam purpose)

While installing Linux you will have the choice of creating new partitions and associating each partition to a mount point (see p.5).

For advanced users this is done in two steps:

1. Use the fdisk tool to create new partitions

2. Associate a mount point to each partition

For intermediate users most distributions include a user friendly tool that does both these steps at once:

diskdrake (Mandrake)

DiskDruid (RedHat)

Finally, for beginners and busy sysadmin’s, the latest Linux distributions will automatically assign a partition scheme.

3. On a Running System:

Once the operating system is installed you can use the fdisk utility to configure new partitions.

We will next look at the basic syntax for fdisk

Example:

1) Start partitioning the first hard drive:

fdisk /dev/hda

2) Type m for help. Then create a new partition with n.

3) To write the changes to disk type w.

4) REBOOT.

These four points outline the steps you would follow to create new partitions. The last point

is often overlooked. This forces the partition table in the master boot record MBR to be reread.

NOTICE
You need to create a filesystem on a new partition with mkfs or mke2fs before using it

This ends the survey of available partitioning tools. We next take a look at bootloaders.

3. Bootloaders

The MBR occupies the first sector of the disk (512 bytes) and contains the partition tables together with a bootloader. At boot time the bootloader reads the partition tables looking for a partition marked “active” and loads the first sector of this partion.

LILO the Linux Bootloader

There are roughly 3 parts involved:

1. LILO

This is the loader itself. LILO is installed on the MBR and loads the second stage bootloader, generally situated in /boot/boot.b.

2. /etc/lilo.conf

The main options are specified here

boot*	where LILO should be installed (/dev/hda is the MBR)

install	which second stage to install (boot.b is the default)

prompt	give the user a chance to choose an OS to boot

default	name of the image that will be booted by default

timeout	used with prompt, causes LILO to pause (units are 1/10 of a sec)

image*	path to the kernel to boot (one can use ‘other’ to chain load)

label*	name of the image. This is the name a user can type at the boot prompt

root*	the name of the disk device which contains the root filesystem /

read-only*	mount the root filesystem read-only for fsck to work properly

append	give kernel parameters for modules that are statically compiled.

linear/lba32	these options are mutually exclusive. Both ask LILO to read the disk using Linear Block Addressing. linear is typically used for very large disks. lba32 is used to allow boot time access to data beyond the first 1024 cylinders (also see p.36)

3. /sbin/lilo

This binary reads it’s configuration file /etc/lilo.conf and installs the LILO bootloader.

/sbin/lilo should be run every time a change is made to /etc/lilo.conf

GRUB the Grand Unified Bootloader

GRUB is also installed on the MBR. You can either alter this MBR with the /sbin/grub shell or use a configuration file called /boot/grub/grub.conf which will be read by /sbin/grub-install

Detailed information about GRUB can be found in the info pages

Main sections in /boot/grub/grub.conf:

1. General/Global

default	image that will boot by default (the first entry is 0)

timeout	prompt timeout in seconds

2. Image

title	name of the image

root	where the 2nd stage bootloader and kernel are e.g (hd0,0) is /dev/hda

kernel	path for the kernel starting from the previous root e.g /vmlinuz

ro	read-only

root	the filesystem root

initrd	path to the initial root disk

Example grub.conf
default=0
timeout=10
splashimage=(hd0,0)/grub/splash.xpm.gz
title Linux (2.4.18-14)
root (hd0,0)
kernel /vmlinuz-2.4.18-14 ro root=/dev/hda5
initrd /initrd-2.4.18-14.img

4. Managed devices

At boot time the /etc/fstab file assigns mount points for block devices.

The /etc/fstab format

device mount-point fstype options dump-number fsck-number

Sample /etc/fstab

LABEL=/	/	ext2	defaults	1 1

LABEL=/boot /boot	ext2	defaults	1 2

LABEL=/home	/home	ext3	defaults	1 2

/dev/fd0	/mnt/floppy auto	noauto,owner	0 0

LABEL=/usr	/usr	ext2	defaults	1 2

LABEL=/var	/var	ext3	defaults	1 2

none	/proc	proc	defaults	0 0

none	/dev/shm	tmpfs	defaults	0 0

none	/dev/pts	devpts gid=5,mode=620	0 0

/dev/hdc9	swap,pri=-1	swap	defaults	0 0

/dev/cdrom /mnt/cdrom iso9660 noauto,owner,kudzu,ro 0 0

The mount command is used to make a particular device available on a specific directory (mount point). The syntax is:

mount -t [FSTYPE] -o [OPTIONS] DEVICE DIRECTORY

For example we can mount a CDROM on the mount point /mnt/cdrom with:

mount -t iso9660 /dev/cdrom /mnt/cdrom

On a running system the /etc/fstab file also acts as a shortcut for assigning a resource to a specific directory. For example:

mount /dev/cdrom

The mount utility reads fstab and deduces where to mount the resource. Notice that some of the devices are accessed using a label. Labels are assigned to devices with the tune2fs tool:

tune2fs -L /usr/local /dev/hdb12

Option summary for mount:
rw,ro	read-write and read-only
noauto	the device is not mounted at boot time
users	the device can be read and unmounted by all users
user	the device can be unmounted only by the user
owner	the device will change it's permission and belong to the user that mounted it
usrquota	start user quotas on the device
grpquota	start group quotas on the device

NOTICE
Remember that mount -a will mount all filesytems in /etc/fstab that have not been mounted and do not have the option noauto

The umount command will unmount a device. Notice that the command is misspelled! The syntax is:

umount DEVICE or MOUNT-POINT

For example the following commands will both unmount the CDROM device:

umount /dev/cdrom

or

umount /mnt/cdrom

5. Quotas

The quota tools allow administrators to set up quotas without having to reboot. Here are the steps.

1. Edit /etc/fstab and add usrquota to the options

2. Remount the partition:

mount -o remount <device>

3. Start the quota stats:

quotacheck -ca

The preliminary aquota.user database file is generated at the top of the directory.

4. Edit quotas for each user:

edquota -u <user>

Here a soft/hard limit must be set for both the number of blocks and inodes available for each user.

The system will allow the user to exceed the soft limit during a certain grace period. After the grace period has expired the soft limit will be enforced as a hard limit.

5. START enforcing quotas:

quotaon –a

Users can query the quota status with quota. The system administrator can generate reports with repquota or quotastats.

6. Exercises and Summary

Review Questions (answers p.150)

Yes or No

1. When LILO is installed and further changes are made to lilo.conf it is

not necessary to re-run /sbin/lilo	______

2. When GRUB is installed and further changes are made to grub.conf it is

not necessary to re-run grub-install	______

3. If /root is beyond the 1024 cylinder limit then a Linux system may not boot	______

4. Quotas may only be used on an entire partition	______

Glossary

Term	Description
partition	an independent section of a hard drive which can either be used to directly store data or can be further divided into (logical) partitions. Since all partitions mounted and manipulated by the operating system have a separate filesystem and are considered as independent devices, a partition is also sometime called a 'device' or even a 'filesystem'
primary (partition)	partition described by one of the original partition record kept in the partition table. Only four such records are available, therefore disks can only have four primary partitions
extended (partition)	a primary partition whose partition record contains a linked list of partition records making it possible to create further partitions called 'logical partitions' as opposed to primary
logical (partition)	a partition contained in an extended partition
MBR	the first sector (512 bytes) of a hard drive which contains the boot loader and the disks partition tables
1024 cylinder limit	when using CHS addressing old BIOS systems would use 10 bits to read the number of cylinders ,8 bits for the heads and 6 bits for the sectors. This would allow access to disks with a maximum size of (2^10)*(2^8)*(2^6-1)*512 bytes which corresponds to 8.5 GB (metric). When running /sbin/lilo addresses are given in CHS form (unless lba32 or linear is used) for the BIOS to read. If the second stage boot loader /boot/boot.b is 'further' than 1024 cylinders away from the MBR then the system will not boot
bootloader	code stored in the first 512 bytes of a disk which is read by the BIOS and used to start an operating system
GRUB	Grand Unified Bootloader
LILO	Linux boot Loader
quotas	mechanism available per device to set restrictions on the amount of inodes and data blocks per user or group
grace	time limit for files and data that have exceeded their soft limit

Files

File	Description
/boot/boot.b	The LILO second stage bootloader
grub.conf	configuration file for GRUB
/etc/fstab	fstab(5) – The file fstab contains descriptive information about the various file systems. fstab is only read by programs, and not written; it is the duty of the system administrator to properly create and maintain this file
/etc/lilo.conf	configuration file read by the bootloader installation mapper /sbin/lilo
/proc/devices	devices found on the system and their associated major number
aquota.user	database file stored on the root of the device where user quotas are inforced

Commands

Command	Description or apropos
/sbin/lilo	lilo(8) – install boot loader
edquota	edquota(8) – edit user quotas
fdisk	fdisk(8) – partition table manipulator for Linux
grub-install	grub-install(8) - install GRUB on your drive
mount	mount(8) – mount a file system
quotas	quota(1) – display disk usage and limits
quotacheck	quotacheck(8) – scan a filesystem for disk usage, create, check and repair quota (database) files
quotaon	quotaon(8) / quotaoff – turn filesystem quotas on and off
quotastats	quotastats(8) – program to query quota statistics
repquota	repquota(8) – summarize quotas for a filesystem
tune2fs	tune2fs(8) – adjust tunable filesystem parameters on second extended filesystems
usrquota,grpquota	(not a command) option set in /etc/fstab to enable quotas on a device
umount	umount(8) – unmount file systems

Exercises

1.	Create 1 new partition on the /dev/hda device using fdisk.

fdisk /dev/hda

HINT:	To create a new partition type n. The partition type defaults to 83 (Linux)

To write the new partition table type w.

The partition table needs to be read: REBOOT the computer !

2.	Make a new filesystem (format) on one of the partitions:

mkfs <device>

3.	(i) Make a directory called data in the root directory.

mkdir /data

(ii) Edit /etc/fstab and allocate the mount point /data to this new resource

<device>	/data	ext2	defaults	0 2

4.	Force mount to read /etc/fstab:

mount –a

If this doesn't work check that each entry is correct in the fstab and make sure that the	directory /data exists (2 (i))

5.	Follow the steps in this chapter to enforce quotas on this device.

After step (2) run the mount command and look at the output. Which option from

/etc/fstab can be seen showing that quotas are availabe on the device? _________

After step (3) which file is created in the /data directory? __________

Before testing quotas for with non-root users, add read-write permissions on /data

chmod o+rw /data

In extreme cases it may be easier to reboot and let the init scripts build the aquota.user	(or aquota.group) file. If nothing is showing with the quotas, repquota, or quotastats	tools make sure you have read-write access for everyone on /data [chmod a+rw /data ]

6.	(OPTIONAL) The instructor computer has a NFS share. Find out which directory is	shared and edit /etc/fstab to mount this share on /mnt/nfs. Use the noauto option fot the	share not to mount at boot time.

7. SWAPPING bootloaders

a. Uninstall LILO from the MBR (or the floppy)

lilo –u

b. Modify the grub.conf sample on p. 28 to reflect your system

c. Install GRUB on the floppy with grub-install /dev/fd0

The Linux Filesystem

Prerequisites

Experience with the Linux installation process (also see the section Installation on p.1)

Goals

Introduce the base directories and concepts from the File System Hierarchy (FHS)

Make a filesystem of any type (e.g EXT2or EXT3) on a partition

Monitor free space per device or directory

Understand the UNIX-like file and directory permissions

Contents

The Linux Filesystem	39

1. The Filesystem Structure	40

2. Formatting and File System Consistency	42

3. Monitoring Disk Usage	45

4. File Permissions and Attributes	46

5. Exercises and Summary	52

1. The Filesystem Structure

A filesystem is similar to a tree structure. The root of the tree is represented at the top and the leaves below.

As mentioned earlier, once partitions have been created each partition must be given a mount point. This is typically done at installation time. To help us understand where things are kept, let us look at the Linux file system hierarchy.

The top of a Linux file system hierarchy starts at root (/). This is similar to C:\ under DOS except that C:\ is also the first device, whereas the root directory can be mounted anywhere.

Figure 1: The base directories

The base directories are the first subdirectories under the root directory. These are installed by an rpm package usually called filesystem.

rpm -ql filesystem

During the booting process the kernel first mounts the root (/) partition. In order to mount and check any further partitions and filesystems a certain number of programs such as fsck, insmod or mount must be available.

	The directories /dev, /bin, /sbin, /etc and /lib must be subdirectories of root (/) and not mounted on separate partitions. Added to this, there must be an empty directory /proc on the root device used by the kernel to report information about the operating system (e.g processes, memory statistics, etc ...)

Base directories:

/bin and /sbin

Contain binaries needed to boot up the system and essential commands.

/dev

Location for device or special files

/etc

Host specific configuration files

/lib

Shared libraries for binaries in /bin and /sbin. Also contains kernel modules

/mnt/ or /media (Suse)

Mount point for external filesystems

/proc

Kernel information. Read-only except for /proc/sys/

/boot

Contains the Linux kernel, the system maps and the “second stage” bootloaders.

/home (optional)

The directories for users. Initially contains the contents from /etc/skel/

/root (optional)

The directory for user root

/tmp

Temporary files

/usr

User Specific Resource. Mainly static and shareable content

/usr/local or /opt (optional)

Add-on software applications. Can also contain shared libraries for add-on software.

/var/www, /var/ftp/ or /srv (Suse)

Location for HTML pages and anonymous FTP directories.

/var

Variable data, such as spools and logs. Contains both shareable (eg. /var/spool/mail) and non-shareable (eg. /var/log/) subdirectories.

2. Formatting and File System Consistency

In order to organise data on a disk partition one needs to create a file system. At installation time you will be asked which type of file system must be used.

Many file system types are supported. The ext2 file system type is the default and is also known as “Linux Native”. In some more recent installers, ext3 is the default. This is really only an ext2 filesystem with a journal patched on top.

A different file system type must be used for SWAP. The file system for Swap is of type swap and cannot be anything else.

The Second Extended File System

Lets take a closer look at the ext2 (second extended) file system. The ext2 consists of blocks of size 1024 bytes =1 KB (default). Without entering into too much detail, there are three types of blocks:

● Superblocks:

Repeated every 8193 blocks. Contains information about block-size, free inodes, last mounted time, etc …

● Inodes:

Contains pointers to data blocks. The first 12 blocks of data are directly accessed. If the data exceeds 12KB, then indirect inodes act as relays.

Each inode is 256 bytes and contains the user, group, permissions and time stamp of the associated data.

● Data Blocks:

These are either files or directories and contain the actual data.

Formatting tools

The file systems supported by the kernel allow one to read from a pre-formatted disk. To create these file systems while running a Linux system one also needs to install the associated formatting tools.

The formatting tool for ext2 is mkfs.ext2 or mke2fs. Similarly the formatting tool for the xfs file system type from Silicon Graphics will be mkfs.xfs and may have to be installed separately.

The mkfs tool acts as a front for all these file system types. The syntax is:

mkfs –t <fstype> <DEVICE>

Notice that the ext3 is an ext2 file system type on which a journaling system has been added (see the exercises for details).

Example 1: Making a jfs filesystem

mkfs –t jfs /dev/hda12

Example 2: Making a ext2 filesystem

mke2fs /dev/hda11 [or mkfs –t ext2 /dev/hda11]

File System Consistency

If the file system is damaged or corrupt, then the fsck utility should be run against the partition (the minimum requirement is that the file system be unmounted or mounted read-only).

fsck acts as a front that automatically detects the file system type of a partition. Then as with mkfs, the tools fsck.ext2, fsck.ext3 will be called accordingly. Since EXT2 is the main filesystem type for Linux there is a e2fsck command that only handles this filesystem type.

You can explicitly specify a file system type with the following syntax:

fsck –t <fstype> <device>

Example: Checking a reiserfs filesystem on the /dev/sdb10 device:

fsck –t reiserfs /dev/sdb10

fsck.reiserfs /dev/sdb10

File System Debug Commands

The debugfs and dumpe2fs are seldom used but can be useful in providing low level information about an ext2 or ext3 filesystem.

debugfs [ -b blocksize ] [ -s superblock ] [ -f cmd_file ] [ -R request ] [ -V ] [ [ -w ] [ -c ] [ -i ] [ device ] ]

The debugfs program is an interactive file system debugger. It can be used to examine and change the state of an ext2/3 file system.

Once in the debugfs shell, internal commands can then be used to change directory, examine inode data, remove files, create links, dump the ext3 journal logs etc. While this is a very powerful command, it should be used with caution, generally only after the fsck command has failed to make any headway.

dumpe2fs [ -bfhixV ] [ -ob superblock ] [ -oB blocksize ] device

dumpe2fs prints the super block and block group information for the filesystem present on device.

dumpe2fs /dev/hda1 dumpe2fs 1.35 (28-Feb-2004) Filesystem volume name: /boot1 Last mounted on: <not available> Filesystem UUID: d741042c-3eaf-49ee-94c1-7dd8c5459764 Filesystem magic number: 0xEF53 Filesystem revision #: 1 (dynamic) Filesystem features: has_journal ext_attr resize_inode dir_index filetype needs_recovery sparse_super Default mount options: (none) Filesystem state: clean Errors behavior: Continue Filesystem OS type: Linux Inode count: 25584 Block count: 102280 Reserved block count: 5114 Free blocks: 80564 Free inodes: 25537 First block: 1 Block size: 1024 Fragment size: 1024 Reserved GDT blocks: 256 Blocks per group: 8192 Fragments per group: 8192 Inodes per group: 1968 Inode blocks per group: 246 Filesystem created: Sat May 7 10:40:51 2005 Last mount time: Sun May 29 04:08:01 2005 Last write time: Sun May 29 04:08:01 2005 Mount count: 10 Maximum mount count: -1 Last checked: Sat May 7 10:40:51 2005 Check interval: 0 (<none>) Reserved blocks uid: 0 (user root) Reserved blocks gid: 0 (group root) First inode: 11 Inode size: 128 Journal inode: 8 Default directory hash: tea Directory Hash Seed: 50108791-6a0a-41ff-9608-0485c993eaf9 Journal backup: inode blocks Group 0: (Blocks 1-8192) Primary superblock at 1, Group descriptors at 2-2 Block bitmap at 259 (+258), Inode bitmap at 260 (+259) Inode table at 261-506 (+260) 0 free blocks, 1942 free inodes, 2 directories Free blocks: Free inodes: 27-1968 [....]

3. Monitoring Disk Usage

Using mount and df:

Both these tools work on a device level, as opposed to a directory level. The mount and umount tools maintain the list of mounted filesystems in /etc/mtab.

Typing mount with no options will show all filesystems currently mounted. The output is similar to /etc/mtab. Notice that the kernel also keeps track of mounted filesystems in /proc/mounts.

In addition to showing all mounted devices the df tool will also show Used and Available disk space. By default this is given in blocks of 1K.

df -h
Filesystem Size Used Avail Use% Mounted on
/dev/hda9 289M 254M 20M 93% /
/dev/hda2 23M 7.5M 14M 35% /boot
none 62M 0 61M 0% /dev/shm
/dev/hda5 1.4G 181M 1.1G 13% /share
/dev/hda7 787M 79M 669M 11% /tmp
/dev/hda3 4.3G 3.4G 813M 81% /usr
/dev/hda6 787M 121M 627M 17% /var
//192.168.123.2/share 12G 8.8G 3.7G 71% /mnt/smb

Using du:

This tool will display disk usage. This is done on a per directory basis. Notice that du cannot display available space since this information is only available at a device level.

The following command will list the current usage of the /etc directory in human readable units (using the -h switch) and will only print the grand total (using the -s switch):

du -sh /etc
62M /etc/

4. File Permissions and Attributes

Changing permissions and owners

From the previous figure we see that permissions can be acted upon with chmod. There are 3 categories of ownership for each file and directory:

u: a valid user with an entry in /etc/passwd

g: a valid group with an entry in /etc/group

o: other

Example:

-rw-rw-r-- 1 jade sales 24880 Oct 25 17:28 libcgic.a

Changing Permissions with chmod:

chmod g=r,o-r libcgic.a chmod g+w libcgic.a

Changing user and group with chown and chgrp :

chown root libcgic.a chgrp apache libcgic.a

NOTICE
A useful option for chmod, chown and chgrp is –R which recursively changes ownership and permissions through all files and directories indicated.

Symbolic and octal notation

Permissions can be read=r, write=w and execute=x. The octal values of these permissions are listed in the next table.

Octal and symbolic permissions.

Symolic	octal	binary
read	4	' 100'
write	2	' 010'
execute	1	' 001'

Permissions apply to the user, the group and to others. An item has a set of 3 grouped permissions for each of these categories.

How to read a 755 or -rwxr-xr-x permission

user	group	other
rwx 4+2+1=7	r_x 4+1=5	r_x 4+1=5

The standard permission

UNIX system create files and directories with standard permissions as follows:

Standard permission for:

Files	666	-rw-rw-rw-

Directories	777	-rwxrwxrwx

Umask

Every user has a defined umask that alters the standard permissions. The umask has an octal value and is subtracted(*) from the octal standard permissions to give the files permission (this permission doesn't have a name and could be called the file's effective permission).

(*) While subtraction works in most cases, it should be noted that technically the standard permissions and the umask are combined as follows:

Final Permissions = Standard Permissions (logical AND) (NOT)Umask

On systems where users belong to separate groups, the umask can have a value of 002.

For systems which place all users in the users group, the umask is likely to be 022.

SUID permissions

An executable can be assigned a special permission which will always make it run as the owner of this file. This permission is called SUID meaning 'set user ID'. It has a symbolic value s or a numerical value 4000.

Administrative tools may have the SUID bit set in order to allow non-root users to change system files.

For example the passwd command can be run by any user and will interactively change his or her current password. This password will be saved to /etc/passwd or /etc/shadow. However both these files belong to user root with typical permissions of 644 and 600 respectively.

This problem has been solved by setting the SUID bit on passwd hence forcing it to run as user root with the correct permissions to modify /etc/passwd or /etc/shadow.

The SUID on passwd

ls -l $(which passwd)
-r-s--x--x 1 root root 18992 Jun 6 2003 /usr/bin/passwd

NOTICE
The SUID bit is shown in symbolic form in the command above. It is possible to get more information about a file using stat as well as seeing the octal representation of the permissions as follows:
stat /usr/bin/passwd
File: `/usr/bin/passwd'
Size: 18992 Blocks: 40 IO Block: 4096 regular file
Device: 305h/773d Inode: 356680 Links: 1
Access: (4511/-r-s--x--x) Uid: ( 0/ root) Gid: ( 0/ root)

WARNING! WARNING! WARNING!
The SUID permission is often associated with security issues. Here is an example that illustrates this.
1. A user would like to read user root' s mail. For this he changes the environmental variable as follows:
export MAIL=/var/spool/mail/root
2. The user then uses the command mail, hoping to see something!
mail
/var/spool/mail/root: Permission denied
So far it doesn't work. This would be too easy!
But if root can be convinced to set the SUID bit on mail the previous commands would allow any user to read anybody's mail (including root).

The next examples are dangerous. Why?

chmod 4755 /bin/cat chmod u+s /bin/grep

SGID permissions

The SGID is a permission similar to SUID that is set for group members. The symbolic value is s and the octal value of 2000.

Setting SGID on a directory changes the group ownership used for files subsequently created in that directory to the directories group ownership. No need to use newgrp to change the effective group of the process prior to file creation (see exercise p.55) .

Examples:

chmod 2755 /home/data chmod g+s /bin/wc

The sticky bit

The sticky bit permission with value 1000 has the following effect:

Applied to a directory it prevents users from deleting files unless they are the owner (ideal for directories shared by a group)

Applied to a file this used to cause the file or executable to be loaded into memory and caused later access or execution to be faster. The symbolic value for an executable file is t while for a non executable file this is T. As file system caching is more generic and faster, file sticky bits tend not be supported any more.

Examples:

chmod 1666 /data/store.txt chmod o+t /bin/bash

File Attributes

Alongside the standard permissions there is another system that can be used to change the way a file can be used. File Attributes do not show up in the 'ls' command. The 'lsattr' command must be used instead. The 'chattr' command is used to set and drop these attributes.

The following attributes are available. Please note the case.

'A' When a file with the ’A’ attribute set is accessed, its atime (access time) record is not modified. This avoids a certain amount of disk I/O, typically for temporary files. Do be aware that some tools, such as tmpwatch, rely on the atime record to determine if the file has been used recently. If the atime record is not being updated the file's status might be misinterpreted.

'a' A file with the ‘a’ attribute set can only be open in append mode for writing. Only the superuser or a process possessing the CAP_LINUX_IMMUTABLE capability can set or clear this attribute. This is probably most effectively used on system log files, to prevent intruders removing evidence of their passage. Do be aware that in order for the intruder to have any chance of editing these log files, they need to have root access. With root access they could remove the 'a' attribute, make the edits and then re-establish the 'a' attribute.

'c' A file with the ‘c’ attribute set is automatically compressed on the disk by the kernel. A read from this file returns uncompressed data. A write to this file compresses data before storing them on the disk. NB Sadly, while the attribute is set on the file and is displayed by the lsattr command, it is not yet honoured by the ext2 or ext3 filesystem kernel drivers.

'D' When a directory with the ‘D’ attribute set is modified, the changes are written synchronously on the disk; this is equivalent to the ‘dirsync’ mount option applied to a subset of the files. When this attribute is in operation against a directory, the following operations are synchronous within that directory: create, link, unlink, symlink, mkdir, rmdir, mknod and rename.

'd' A file with the ‘d’ attribute set is not candidate for backup when the dump (8) program is run.

'i' A file with the ‘i’ (immutable) attribute cannot be modified: it cannot be deleted or renamed, no link can be created to this file and no data can be written to the file. Only the superuser or a process possessing the CAP_LINUX_IMMUTABLE capability can set or clear this attribute.

'j' A file with the ‘j’ attribute has all of its data written to the ext3 journal before being written to the file itself, if the filesystem is mounted with the "data=ordered" or "data=writeback" options. When the filesystem is mounted with the "data=journal" option all file data is already journalled and this attribute has no effect. Only the superuser or a process possessing the CAP_SYS_RESOURCE capability can set or clear this attribute.

's' When a file with the ‘s’ attribute set is deleted, its blocks are zeroed and written back to the disk. NB As with the 'c' attribute, this attribute is honoured by everything except the kernel filesystem driver.

'S' When a file with the ‘S’ attribute set is modified, the changes are written synchronously on the disk; this is equivalent to the ‘sync’ mount option applied to a subset of the files. It is most often used for the 'cooked files' used by database programs to hold their data. When used in this way the addition of two different caching systems together is avoided. The caching system of the database, which is optimised for that systems use of data, is allowed to write direct to disk.

'T' The 'T' attribute is only usable when using the 2.6.x kernel. The 'T' attribute is designed to indicate the top of directory hierarchies, this is designed for use by the Orlov block allocator. The newer file allocation policies of the ext2 and ext3 filesystems place subdirectories closer together allowing faster use of a directory tree if that directory tree was created with a 2.6 kernel.

't' A file with the ’t’ attribute will not have a partial block fragment at the end of the file merged with other files (for those filesystems which support tail-merging). This is necessary for applications such as LILO which read the filesystems directly, and which don’t understand tail-merged files. Note: As of this writing, the ext2 or ext3 filesystems do not (yet, except in very experimental patches) support tail-merging.

'u' When a file with the ‘u’ attribute set is deleted, its contents are saved. This allows the user to ask for its undeletion. This is another attribute that is supported by everything except the kernel itself.

Example:

# lsattr testfile ------------- testfile # chattr +i testfile # lsattr testfile ----i-------- testfile # rm -f testfile rm: cannot remove `testfile': Operation not permitted # chattr -i testfile # rm -f testfile # ls testfile ls: testfile: No such file or directory

5. Exercises and Summary

Review Questions (answers p.150)

Yes or No

1. The /usr directory must always be on the root device since it contains

essential tools needed at boot time	_____

2. If a user's home directory is anywhere else than in the /home directory

then some operations may not work	_____

3. Making a filesystem on a partition always deletes all the data on that partition	_____

Glossary

Term	Description
base directories	subdirectories that are directly under the root directory
data block	block used to store data on a filesystem. Data blocks are referenced by inodes
essential root (/) subdirectories	term used in this manual to identify directories that must be present at boot time once the root filesystem has been mounted
ext2	the second extended filesytem type was adopted as the generic Linux filesystem
ext3	the third extended filesystem supports the same features as ext2 with an added journalling system
file permissions	attributes stored inside a file's inode giving simple read,write and execute permissions to the file owner (u), the group (g) and any other (o) user as well as more advanced permissions such as SUID, SGID and the 'sticky bit'
filesystem hierarchy standard (FHS)	"This standard consists of a set of requirements and guidelines for file and directory placement under UNIX-like operating systems. The guidelines are intended to support interoperability of applications, system administration tools, development tools, and scripts as well as greater uniformity of documentation for these systems" – see http://www.pathname.com/fhs/
inode	block used to store information about files, directories and symbolic links. Information includes the location of the file's data block, file permissions, time stamps and file type (e.g directory, file or symlink)
Orlov block allocator	Scheme that increases the performance of an EXT2/EXT3 filesystem. It is only available for 2.6 kernels. It was ported from BSD and improved by Alexander Viro, Andrew Morton, and Ted Ts'o. The original author is Grigory Orlov. This scheme can be switched on and of using the chattr command under Linux
superblock	is read when the filesystem is mounted, contains information such as the block-size used for the current filesystem (default 1024), the number of free inodes, the mount count and maximum mount count (used to determine if a full filesystem check should be performed)

Files

File	Description
/etc/mtab	file used by mount to keep track of currently mounted devices
/proc/mounts	file used by the kernel to keep track of currently mounted devices

Commands

Command	Description (apropos)
chattr	changes file attributes on a ext2/3 filesystem
chgrp	chgrp - change the group ownership of a file
chmod	chmod – change file access permission
chown	chown(1) – change the user and group ownership of a file
df	df - report filesystem disk space usage
du	du - estimate file space usage
e2fsck	e2fsck - check and repair a Linux second extended file system
fsck	check and repair any file system
lsattr	lists the file attributes on a ext2/3 filesystem
mke2fs	mke2fs – create an ext2/3 filesystem
mkfs	mkfs – build a Linux file system
mount	mount(1) – All files accessible in a Unix system are arranged in one big tree, the file hierarchy, rooted at /. These files can be spread out over several devices. The mount command serves to attach the file system found on some device to the big file tree. Conversely, the umount(8) command will detach it again
umask	tool used to set the file-creation mask mode – see help umask

Filesystem

1.	Create 2 new partitions (larger than 50M) on the /dev/hda device using fdisk.

HINT: To create a new partition type n. The partition type defaults to 83 (Linux)

To write the new partition table type w.

The partition table needs to be read: REBOOT the computer !

2.	Format the first partition using the ext2 filesystem type and the second with reiserfs.

HINT: The mkfs tool is a front for mkfs.ext2 or mkfs.reiserfs, etc. The syntax is

mkfs –t <fstype> <device>

3.	Make directories in /mnt and mount the new partitions

mkdir /mnt/ext2

mkdir /mnt/reiserfs

4.	Check the status of your system:

Use mount to verify which devices are mounted. The permissions set in fstab are visible too.

Use df to check the total number of blocks used. The –k option will convert the number of blocks in	kilobytes (the default block size for ext2)

Run fsck on one of the newly created filesystems. The fsck utility is a front for fsck.ext2, fsck.ext3,	fsck.reiserfs, etc. The syntax is:

fsck	<device>

5.	Going further: Changing from ext2 to ext3 :

Update the device mounted on /mnt/ext2 to ext3 with tune2fs. This will add a journal to the existing	filsystem. Make sure to make the relevant change for the filesystem type in /etc/fstab

tune2fs –j /dev/hdaN

At this stage the system has added a journal to the /dev/hda10 partition, making it an ext3 formated partition. This process is non-destructive and reversible. If you mount an ext3 as an ext2 filesystem, the .journal file will be erased. You can add it again with tune2fs …

File permissions

1.	Login as a user (non root). Create a file using touch and verify that it has the effective permission 664.

2.	Change the umask to 027. If you create a new file what is it’s effective permission? _________

Where is the value of umask set? Depening the systems this can be /etc/profile or /etc/bashrc

3.	Add 2 users to your system.

useradd user1

useradd user2

Add passords with passwd user1 and passwd user2

4.	Create a group called sales.

groupadd sales

5.	Add the users to the group sales

gpasswd -a user1 sales

gpasswd -a user2 sales

6.	Create a directory /news owned by the group sales and read-writable for this group.

mkdir -m 770 /news ; chown .sales /news

7.	Set the GID to the /news directory.

chmod g+s /news

What are the symbolic permissions (eg. -rwxr_xr_x) on /news? [use ls -ld /news ] ______

Verify that a group member doesn’t need to type “newgrp sales” in order to create files with the right permissions. Can members of the group sales modify any files in this directory?

8.	Add the sticky-bit permission on the /news directory. Verify that only user-owners can modify the files	in the that directory. What are the permissions like on /news? ______________

10.	As root set SUID root xeyes. Login as a non root user. Check that this binary runs with UI root.

chmod u+s `which xeyes`

Log in as another user and run xeyes. Then do:

ps aux | grep xeyes

(the binary should be running as root)

The Command Line

Prerequisites

None

Goals

Introduce the bash shell and basic concepts such as interactively starting an executable

Distinguish variables defined as local or global (exported)

Manipulate data streams using pipes and other redirection operators

Understand meta-characters used for "file globbing"

Contents

The Command Line	56

1. The interactive shell	57

2. Variables	58

3. Input, Output, Redirection	59

4. Metacharacters and Quotes	62

5. The Command History	63

6. Other Commands	64

7. Exercise and Summary	67

Overview

A basic way to interact with a computer system is to use the command line. The shell interprets the instructions typed in at the keyboard. The shell prompt (ending with $ or # for user root) indicates that it is ready for user input.

The shell is also a programming environment which can be used to perform automated tasks. Shell programs are called scripts.

Most Common shells
The Bourne shell	/bin/sh
The Bourne again shell	/bin/bash
The Korn shell	/bin/ksh
The C shell	/bin/csh
Tom's C shell	/bin/tcsh

Since the bash shell is one of the most widely used shells in the Linux world the LPI concentrates mainly on this shell.

1. The interactive shell

Shell commands are often of the form

command [options] {arguments}.

Printing text to the screen

The the bash shell uses the echo command to print text to the screen.

echo “this is a short line”

Full/Relative path

The shell interprets the first ¨word¨ of any string given on the command line as a command. If the string is a full or relative path to an executable then the executable is started. If the first word has no ¨/¨ characters, then the shell will scan directories defined in the PATH variable and attempt to run the first command matching the string.

For example if the PATH variable only contains the directories /bin and /usr/bin then the string xeyes won't be found since it is stored in /usr/X11R6/bin/xeyes so the full path needs to be run

/usr/X11R6/bin/xeyes

An alternative to typing the full path to an executable is to use a relative path. For example, if the user is in the directory where the xeyes program is stored then one can type

./xeyes

2. Variables

Shell variables are similar to variables used in any computing language. Variable names are limited to alphanumeric characters. For example CREDIT=300 simply assigns the value 300 to the variable named CREDIT.

1. initialise a variable:	Variable-Name=value (no spaces !!)
2. reference a variable:	$Variable-Name

CREDIT=300 echo $CREDIT

The value of a variable can be removed with the unset command.

Export, Set and Env:

There are two types of variable: local and exported.

Local variables will be accessible only to the current shell. On the other hand, exported variables are accessible by both the shell and any child process started from that shell.

The commands set and env are used to list defined variables

The set and env commands
set	Lists all variables
env	Lists all exported variables

A global variable is global in the sense that any child process can reference it.

export VAR=val

LOCAL	EXPORTED
child parent VAR = ?? VAR=val	parent child VAR = val

Example: Make the CREDIT variable a global variable. Test whether it's listed with set or env.

export CREDIT
env | grep CREDIT

Start a new shell (child process) and verify that CREDIT is accessible. Can one start any shell and be sure that CREDIT is still declared ?

List of common predefined variables

PREDEFINED VARIABLES	MEANING
DISPLAY	Used by X to identify where to run a client application
HISTFILE	Path to the users .bash_history file
HOME	The path to the user's home
LOGNAME	The name used by the user to log in
PATH	List of directories searched by the shell for programs to be executed when a command is entered without a path.
PWD	The current working directory
SHELL	The shell used (bash in most Linux distributions)
TERM	The current terminal emulation

Special variables

The next few variables are related to process management.

$! represents the PID value of the last child process $$ represents the PID of the running shell $? is 0 if the last command was executed successfully and 1 otherwise

3. Input, Output, Redirection

UNIX processes normally open three standard file descriptors which enable it to process input and output. These standard descriptors can be redefined for any given process. In most cases the stdin descriptor is the keyboard, and the two output descriptors, stdout and stderr, is the screen.

A process and it’s 3 descriptors
STDOUT > >> | STDIN < STDERR 2>

Numerical values for stdin, stderr and stdout
stdin	0
stdout	1
stderr	2

stdout redirection

program > file

The data flows from left to right.

fdisk –l > partions.txt

This will run the fdisk utility and output the result to the partitions.txt file. No output is visible. Also notice that the shell will read this line from the right. As a result, the

partitions.txt file will be created first if it doesn’t exist and overwritten if the ‘>’ operator is used.

The ‘>>’ operator will append standard output to a file.

STDOUT Redirection
> >> 1> process FILE / DEVICE

stdin redirection

program < file

In this case data flows from right to left. The ‘<’ operator is only used for stdin and cannot be used for stdout.

If the file instuctions contains on each line the letters p, m, and q then the next example would cause fdisk to print the partition table of /dev/hda, print the utility’s help screen and finally quit:

fdisk /dev/hda < instructions

STDIN Redirection
< 0< process FILE / DEVICE

stderr redirection

program 2> errorfile

stdin, stdout and stderr are represented by 0, 1 and 2 respectively. This allows one to select the stderr stream:

find / 2> /dev/null

STDERR Redirection
2> process FILE / DEVICE

piped commands

program1 | program2

Pipes are represented by the “|” symbol. The data stream goes from the left to the right. The next figure illustrates how the stdout for one process is redirected to the stdin for another process.

Piped Commands
| process process

cat /var/log/messages | less

NB Multiple output redirects are parsed from right to left, so the following commands are not equivalent.

Do-command 2>&1 >logfile

Do-command >logfile 2>&1

The tee Command

command | tee FILENAME

This command is used after a pipe and takes a filename as an argument. The standard output from the previous command is then sent to the file given as an argument but tee also lets the stream through to stdout. The stdout has been duplicated in this way.

4. Metacharacters and Quotes

Metacharacters are characters that have special meaning for the shell. They are mainly used for file globbing, that is to match several files or directory names using a minimum of letters.

The input (<), output (>) and pipe (|) characters are also special characters as well as the dollar ($) sign used for variables. We will not list them here but note that these characters are seldom used to name regular files.

Wildcards

● The * wildcard can replace any number of characters.

ls /usr/bin/b* lists all programs starting with a 'b'

● The ? wildcard replaces any one character.

ls /usr/bin/?b* lists all programs having a 'b' as the second letter

● [ ] is used to define a range of value.

ls a[0-9] lists all files starting with an 'a' and have a digit in second position. Also ls [!Aa]* lists all files that don't start with an 'a' or an 'A'

● {string1,string2}; although not just a file naming wildcard, it can be used to match the names of existing files.

ls index.{htm,html}

Quotes and escape codes

The special meaning of metacharacters can be cancelled by escape characters, which are also metacharacters.

The backslash (\) is called the escape character and cancels the meaning of all metacharacters forcing the shell to interpret them literally.

The single quotes (' ') cancel the meaning of all metacharacters except the backslash.

The double quotes (" ") are the weakest quotes but cancel most of the special meaning of the enclosed characters except the pipe (|), the backslash (\) and a variable ($var).

The back tick

Back quotes `` will execute a command enclosed. The next example defines the variable TIME using the date command.

TIME="Today's date is `date +%a:%d:%b`” echo $TIME Today's date is Sun:15:Jul

Another way of executing commands (similar to the back ticks) is to use $(). This will execute the enclosed command and treat it as a variable.

TIME=$(date)

5. The Command History

To view the list of previously typed commands you can use the bash built-in command history.

history ls grep 500 /etc/passwd

This has listed all the cached commands as well as the commands save in ~/.bash_history. When a user exits the shell cached commands are saved to ~/.bash_history.

You can recall commands by using the Up-arrow and Down-arrow on your keyboard. There are also emacs key bindings that enable you to execute and even edit these lines.

Emacs Key Bindings for Editing the Command History
Ctrl+P	Previous line (same as Up-arrow)
Ctrl+n	Next line (same as Down-arrow)
Ctrl+b	Go back one character on the line (same as Left-Arrow)
Ctrl+f	Go forward one character on the line (Same as Right-Arrow)
Ctrl+a	Go to the beginning of the line (Same as <Home>)
Ctrl+e	Go to the end of the line (Same as <End>)

The bang ! key can be used to rerun a command.

Example

!x executes the latest command in the history list starting with an 'x' !2 runs command number 2 from the history output !-2 runs the command before last !! runs the last command ^string1^string2 run previous command and replace string1 by string2

6. Other Commands

Aliases

You can create aliases for commands needing many arguments. The format to create an alias is

alias myprog='command [options]{arguments}'

By typing alias alone at the command line you will get a list of currently defined aliases.

Command completion

By pressing TAB, the shell will complete the commands you have started typing in.

<< is a redirection for EOF

For example

cat << stop

will accept standard input until the keyword 'stop' is entered.

Compound commands

command1; command2; command3	The three commands are run in sequence regardless of the success of the previous command
command1 && command2 && command3	Each command will execute only if the previous exit code is 0 (success)
command1 || comand2 || command3	The next command will execute only if the previous exit code is not 0 (failure)

The ''exec' command

This command is not a binary but rather is part of the shell. It is used to start other commands. Ordinarily if a command is executed, a sub-process is started. If the exec command is used to initiate the new program, it reoccupies the process used to start it. It replaces the current shell (in a script or the interactive shell).

When the new command terminates, control is not passed back to the calling shell, but returns to the process that called the shell used to make the exec call.

echo $$ 414 $ bash $ echo $$ 455 $ echo hello hello $ echo $$ 455 $ exec echo hello hello $ echo $$ 414

The above shows control falling back to the second shell (process 455) after a straight forward echo and the first shell (process 414) using an exec.

Manpages and the whatis database

The manpages are organised in sections
NAME	the name of the item followed by a short one line description.
SYNOPSYS	the syntax for the command
DESCRIPTION	a longer description
OPTIONS	a review of all possible options and their function
FILES	files that are related to the current item (configuration files etc)
SEE ALSO	other manpages related to the current topic

These are the main sections one can expect to find in a manpage.

The whatis database stores the NAME section of all the manpages on the system. This is done through a daily cron. The whatis database has the following two entries:

name(key) – one line description

The syntax for whatis is:

whatis <string>

The output is the full NAME section of the manpages where string matched named(key)

One can also use the man command to query the whatis database. The syntax is

man -k <string>

This command is similar to apropos. Unlike whatis this will query both the “name” and the “one line description” entries of the database. If the string matches a word in any of these fields the above query will return the full NAME section.

Example: (the matching string has been highlighted)

whatis lilo
lilo (8) - install boot loader
lilo.conf [lilo] (5) - configuration file for lilo

man -k lilo
grubby (8) - command line tool for configuring grub, lilo, and elilo
lilo (8) - install boot loader
lilo.conf [lilo] (5) - configuration file for lilo

The FHS recommends manpages to be kept in /usr/share/man. However additional locations can be searched using the MANPATH environment variable set in /etc/man.config. Each directory is further divided into subdirectories corresponding to manpage sections.

Manpage Sections
Section 1	Information on executables
Section 2	System calls, e.g mkdir(2)
Section 3	Library calls, e.g stdio(3)
Section 4	Devices (files in /dev)
Section 5	Configuration files and formats
Section 6	Games
Section 7	Macro packages
Section 8	Administration commands
Section 9	Kernel routines

To access a specific section N one has to enter:

man N command

Examples:

man mkdir
man 2 mkdir

man crontab
man 5 crontab

7. Exercise and Summary

Review Questions (answers p.150)

Yes or No

1. If the PATH variable isn't properly set then programs can be

started only if users type in the executable's full or relative path	_____

2. The STDOUT from a process can be piped into a file	_____

3. Once a data stream has gone through a pipe that stream is

generally no longer visible on STDOUT	_____

4. All the commands entered at the shell are stored in a mysql database	_____

Glossary

Term	Description
compound commands	several commands given in a single line at the shell using delimiters. Depending on the delimiter the shell will execute the commands differently (p.64)
metacharacters	character that is not interpreted literally by the shell but has added meaning
command substitution	use the output of a command as a variable. This is done by enclosing the command in back ticks `` or round brackets $() For example ls /home/$(whoami) will list the current user's home directory
file globbing	term used when handling multiple file names using wild cards. The name comes from the glob sub-program in old UNIX shells used to expand wild cards given on the command line
redirection and pipes	operations that manipulate data streams and the file descriptors of a process. A redirection involves a process and a file, whereas a pipe will involve only processes
stderr, stdin, stdout	names of the file descriptors available for any process to stream error messages, read input streams and write output (non-error) streams
wild cards	the following *, ? , "{}" or "[ ]" metacharacters used to match more than one character when working on the command line

Commands

Command	Description (or apropos)
alias	set an alias for a single or a sequence of commands (see man builtins or help alias)
echo	print text to STDOUT
env	list variables that have been exported (see man builtins or help env)
exec	Shell built-in used to execute new programs but instead of starting a new sub-process it replaces the calling process
export	export the value of a variable to the environment of subsequently executed commands (see man builtins or help export)
history	display the command history list with line numbers (see man builtins or help history)
tee	tee(1) – read from standard input and write to (both) standard output and files
set	list all variables in the environment of the current process (see also man builtins and help set)

Exercises

WARNING: You will need the uuencode and uudecode commands in the exercises. These commands are provided by the sharutils package.

Stdin-stdout-stderr

Type the next commands and represent the sequence of execution (if possible) using diagrams similar to the ones used in this chapter.

ls /etc ; df > /tmp/out.1 (ls /etc ; df) > /tmp/out.2 find /etc -type f 2> /dev/null | sort tr [a-z] [A-Z] < /etc/passwd | sort > /tmp/passwd.tmp cat /tmp/passwd.tmp | tr [A-Z] [a-z]

Command Line

1. List all files in /usr/X11R6/bin that don't start with an x

ls /usr/X11R6/bin/[!x]*

2. The command xterm has the following options:

-bg <color>	set background

-fg <color>	set foreground

-e <command>	execute ‘command’ in terminal

Set a new alias such that the su command opens a new color xterm and prompts for a root	password.

alias su=”xterm -bg orange -fg brown -e su - &”

Where would you store this alias on the system? ___________

3. You can encode files using uuencode. The encoded file is redirected to stdout.

For example: uuencode /bin/bash super-shell > uufile encodes /bin/bash and will produce a file called super-shell when running uudecode against the uufile

Mail the uuencoded /bin/bash to a local user (for this you can either use uuencode and a pipe | , or save the uuencoded output to a file uufile and use STDIN redirection <).

Split the uuencoded file into 5 files:

uuencode /bin/bash super-shell > uufile

split –b 150000 uufile base-name.

This will create files called base-name.aa, base-name.ab, etc

To get a uuencoded file with all the original data (unsplit) do

cat base-name.* > uufile.new

Finally uudecode the file and check it still works.

uudecode uufile.new

This should create a binary file called super-shell

3. Which tool finds the full path to a binary by scanning the PATH variable? _____

Variables

1. Do the following

Assign the value ‘virus’ to the variable ALERT.

ALERT=virus

Verify that it is defined using the set command:

set |grep ALERT

Is ALERT listed when using env instead of set?

Next type ‘bash’. Can you access the ALERT variable?

bash

echo $ALERT

NOTE the value of ALERT: ______ ( is it blank?)

Type exit (or ^D) to return to your original session.

Use the export command to make ALERT a global variable.

export ALERT

Verify that it is a global (env) variable

env | grep ALERT

Start a new bash shell and make sure that ALERT is defined in the new shell:

bash

echo $ALERT

In this new shell, redefine the variable ALERT

export ALERT=green

Exit that shell. What is the value of ALERT in the original shell? ________

2. At the command prompt type the following lines:

CREDIT01=300;CREDIT02=400

for VAR in CREDIT01 CREDIT02;do echo $VAR;done

Notice that the variable VAR is referenced with $VAR.

(i) Rerun this command.

(ii) Rerun this command replacing CREDIT01 by $CREDIT01

3. Using appropriate quotes change your PS1 variable to include the full path to your working directory.

(Hint: the value of PS1 is [\u@ \W]\$ , you only need to replace the \W by a \w)

PS1='[\u@\h \w ]\$ '

What does PS2 look like? ________

File Management

Prerequisites

The Command Line (see p.56)

Understand the EXT2 file system (see p.42)

Goals

Effectively move around the filesystem to create, delete and find files or directories

Distinguish between hard and symbolic links

Contents

File Management	71

1. Moving around the filesystem	72

2. Finding Files and Directories	72

3. Handling directories	74

4. Using cp and mv	74

5. Hard Links and Symbolic Links	75

7. Touching and dd-ing	76

8. Exercises and Summary	78

1. Moving around the filesystem

Absolute and relative paths

A directory or a file can be accessed by giving its full pathname, starting at the root (/) or its relative path, starting from the current directory.

Absolute path:	independent of the user's current directory

starts with /

Relative path:	depends on where the user is

doesn't start with /

As in any structured filesystem there are a number of utilities that can help you navigate through the system. The next two commands are built-in commands.

pwd:	Gives your actual position as an absolute path.

cd:	The 'change directory' command

2. Finding Files and Directories

We will describe the find, which, whereis and locate utilities.

find

Syntax:

find <DIRECTORY> <CRITERIA> [-exec <COMMAND> {} \;]

The DIRECTORY argument tells find where to start searching and CRITERIA can be the name of a file or directory we are looking for.

Examples:

find /usr/X11R6/bin -name ¨x*¨. find / -user 502

Matching lines are listed to standard out. This output can be acted upon. For example delete the file, or change the permission. The find tool has the build-in option –exec which allows you to do that. For example, remove all files belonging to user 502:

find / -type f -user 502 –exec rm –f {} \;

xargs

This tool is often thought of as a companion tool to find. In fact xargs will process each line of standard output as an argument for another tool. We could use xargs to delete all files belonging to a user with:

find / -type f -user 502 | xargs rm –f

	Certain commands such as rm cannot deal with too long arguments. It is sometimes necessary to delete all files in a directory with

ls |xargs rm -f

Common criteria switches for find
-type	specify the type of file
-name	name of the file
-user	user owner
-atime, ctime, mtime	access, creation and modified times (multiples of 24 hrs)
-amin, cmin, mmin	access, creation and modified times (multiples of 1 min)
-newer FILE	files newer than FILE

locate

Syntax:

locate <STRING>

When using locate all files and directories that match the expression are listed.

locate X11R

The search is much faster. In fact locate queries the /var/lib/slocate/slocate.db database. This database is kept up to date via a daily cron job which runs updatedb.

When running updatedb from the command line the /etc/updatedb.conf file is read to determine pruned files systems (e.g NFS) and directories (e.g /tmp)

which

Syntax:

which string

This tool will return the full path to the file called string by scanning the directories defined in the user's PATH variable only. As a result which is only used to find commands.

whereis

Syntax

whereis string

This tool will return the full path to source or binaries as well as documentation files matching string by scanning the PATH variable as well as a number of well known locations

Getting the most from ls

Most common options for ls
-I	show inode
-h	print human readable sizes
-n	list UIDs and GIDs
-p	append descriptor (/=@) to list
-R	recursively display content of directories
-S	sort by file size
-t	sort by modification time (similar to -c)
-u	show last access time

3. Handling directories

Making a directory with mkdir:

When making a directory you can set the permission mode with the -m option. Another useful option is -p which creates all subdirectories automatically as needed.

Example:

mkdir –p docs/programs/versions

Removing directories:

To remove a directory use either rmdir or rm -r. If you are root you may have to specify -f to force the deletion of all files.

Notice:	rm –rf /dir1/* removes all files and subdirectories leaving dir1 empty

rm –rf /dir1/ removes all files and subdirectories including dir1

4. Using cp and mv

cp

Syntax:

cp [options] file1 file2

cp [options] files directory

It is important to notice that cp file1 file2 makes a new copy of file1 and leaves file1 unchanged.

Fig: file1 with inode 250 is copied to file2, duplicating the data to a new data area and creating a new inode 6238 for file2

I D 250 I D 6238

You can also copy several files to a directory, using a list or wildcards. The following table lists the most used options.

Most common options for cp
-d	do not follow symbolic link (when used with -R)
-f	force
-I	interactive, prompt before overwrite
-p	preserve file attributes
-R	recursively copy directories

Note:	cp –r /dir/* /dir2/ will copy all files and subdirectories omitting mydir

cp –r /mydir/ /dir2/ will copy all files and subdirectories including mydir

mv

Syntax:

mv [options] oldname newname

mv [options] source destination

mv [options] source directory

The mv command can both move and rename files and directories. If oldname is a file and newname is a directory then the file oldname is moved to that directory.

If the source and destination are on the same filesystem, then the file isn't copied but the inode information is updated to specify the new location. Most common options are -f force overwrite and -i query interactively.

5. Hard Links and Symbolic Links

Symbolic links

A soft link to a file or a directory creates a new inode that points to the same data area:

ln -s lilo.conf lilo.sym

This is the listing for these files. Notice that the reference count is 1 for both files.

-rw------- 1 root root 223 Nov 9 09:06 lilo.conf

lrwxrwxrwx 1 root root 9 Nov 9 09:06 lilo.sym -> lilo.conf

Fig2: A soft link to a file

I D lilo.conf I lilo.sym

Soft links can be created across filesystems.

Hard Links

A hard link is an additional name for the same inode and as such the reference count of the file increases by one for every new hard link.

ln lilo.conf lilo.link

In the listing notice that the reference count is 2 and that both files have the same size. In fact they are identical.

-rw------- 2 root root 223 Nov 9 09:06 lilo.conf

-rw------- 2 root root 223 Nov 9 09:06 lilo.link

Hard links can only be created within the same filesystem.

7. Touching and dd-ing

touch

Another way of creating or modifying a file is to use touch.

Syntax:	touch {options} file(s)

If file doesn't exist it is created. You can also change the access time of a file using the -a option, -m changes the modification time and -r is used to apply the time attributes of another file.

Example:

touch file1.txt file2.txt	creates new files

touch myfile -r /etc/lilo.conf	myfile gets the time attributes of lilo.conf

 To create a file called –errors use the – option:

touch -- -errors

dd

This command copies a file with a changeable I/O block size. It can also be used to perform conversions (similar to tr). Main options are if= (input file) of= (output file) conv= (conversion)

The conversion switch can be: lcase ucase ascii

Example:

dd if=/mnt/cdrom/images/boot.img of=/dev/fd0

Notice that unlike cp the dd tool will copy portions of a device and preserve the underlying filesystem. On the other hand cp only deals with the data and will transfer it from one filesystem to another:

SOURCE TARGET
cp:
dd: input file = device output file = device
dd: input file = file output file = device
dd: input file = device output file = file
Filesystem A
Filesystem B

8. Exercises and Summary

Review	Questions (answers p.150)

Yes or No

1. The cd – command will take you back to a previous directory?	_____

2. Typing cd ~ (in the bash shell) is the shortest command that will take

you to your home directory ?	_____

3. One can make two new directories /dir1/dir2 using mkdir without any options	_____

4. The command updatedb will update the locate database	_____

5. The syntax to create a symbolic link called FILE-LINK pointing to the file FILE is

ln -s FILE-LINK	FILE	_____

6. The commands cd /etc and cd ./etc are always equivalent	_____

Files

File	Description
/etc/updatedb.conf	configuration file for the updatedb tool
/var/lib/slocate/slocate.db	the locate (or slocate 'secure locate') database

Commands

Command	Description (apropos)
cd	change current directory – see help cd
cp	cp(1) – copy files and directories
dd	copy and convert files. Often used to copy the content of a disk device to another device or file
find	find(1) – search for files in a directory hierarchy
ln	ln(1) – make links between files
locate	command used to search files and directories in the locate database
ls	ls(1) – list directory contents
mkdir	mkdir(1) – make directories
mv	mv(1) – move (rename) files
pwd	pwd(1) – print name of current/working directory
rm	rm(1) – remove files or directories
touch	create new empty file or change file timestamps
updatedb	command used to update the locate database
whereis	whereis(1) – locate the binary, source, and manual page files for a command
which	which(1) – shows the full path of (shell) commands

Exercises

File Navigation

1. Make a new directory in /tmp called /etc.

mkdir /tmp/etc

2. In /tmp/etc/ create a file called newfile (use touch, cat or vi).

3. Go to the root directory (cd /).

4. Test which of the following commands will show the content of newfile ?

cat etc/newfile

cat /etc/newfile

cat tmp/etc/newfile

cat /tmp/etc/newfile

5. Remove the /tmp/etc directory with rmdir. Do step 1 again then remove /tmp/etc with rm

Making space on the filesystem

In order to create more space on the device containing the directory /usr/share/doc we need to find a spare device with enough space and copy the contents of /usr/share/doc to that device. Then we create space by deleting the /usr/share/doc directory and creating a symbolic link from /usr/share/doc to the new location.

6. Make a directory called /spare on which we will mount a spare devices (one of the partitions created in the previous exercises should be suitable)

mkdir /spare

mount <device> /spare

7. Test with df -h /spare and du -hs /usr/share/doc that the device is large enough to contain all of the existing data.

8. Next, copy the contents of /usr/share/doc to /spare/

cp -a /usr/share/doc /spare

9. Make sure the data has all been copied across then edit /etc/fstab to make that device available at boot time.

10. Delete /usr/share/doc and create a symbolic link pointing from /usr/share/doc to /spare/doc

ln -s /spare/doc /usr/share/doc

11. (optional) Do the same with /home. Any extra problems?

Finding Files on the System

12. Copy the file /etc/lilo.conf to /etc/lilo.conf.bak

(i) Use find to find this new file

(ii) Use locate to find /etc/lilo.conf.bak.

(iii) Update the locate database and retry (ii)

Backup strategy (first step)

Find all files in your home directory that have been modified in the past 24 hours.

find /home –mtime –1 |tee list1 |wc –-lines (-1 means less than one day)

We will introduce archiving tools in LPI 102, but the output of the find command can be piped directly into cpio.

Process Management

Prerequisites

The Command Line (p.56)

Goals

Find the process ID (or PID) of a running process using different tools

Use kill and killall effectively with the appropriate signal

Manage jobs from the command line in the foreground or the background

Contents

Process Management	81

1. Viewing running processes	82

2. Modifying Processes	83

3. Processes and the shell	85

4. Exercises and Summary	87

1. Viewing running processes

Processes have a unique Process ID the PID. This number can be used to modify a process' priority or to stop it.

A process is any running executable. If process_2 has been spawned by process_1, it is called a child process. The spawning process_1 is called the parent process.

The process family tree

The pstree command gives a good illustration of parent and child process hierarchy.

Figure 1: Part of the pstree output

bash(1046)---xinit(1085)-+-X(1086) `-xfwm(1094)-+-xfce(1100)---xterm(1111)---bash(1113)-+-pstree(1180) | |-soffice.bin(1139)---soffice.bin(1152)-+ -soffice.bin(1153) | | |-soffice.bin(1154) | | |-soffice.bin(1155) | | |-soffice.bin(1156) | | `-soffice.bin(1157) | `-xclock(1138) |-xfgnome(1109) |-xfpager(1108) |-xfsound(1107) `-xscreensaver(1098)

In the above figure all the process' PIDs are shown; these are clearly incremental. The most common used options are -p to display PIDs and -h to highlight a users processes only.

Finding running processes

A more direct way to determine which processes are running is to use ps. Most users have a set combination of options which work for most situations.

Here are three such options:

ps ux	all processes run by the user

ps T	processes run under the current terminal by the user

ps aux	all processes on the system

It is recommended you read the ps manpage and choose your own best options!

ps accommodates UNIX-style and BSD-style arguments
usage: ps -[Unix98 options] ps [BSD-style options] ps --[GNU-style long options] ps –help for a command summary

Summary of options
-a show all processes for the current user linked to a tty (except the session leader) -e or -A show all processes -f gives the PPID (Parent Process ID) and the STIME (Start Time) -l is similar to -f and displays a long list a show all processes linked to a tty, including other users x show all processes without a controlling tty as well

Continuously updating process information

The top utility will update information on processes at an adjustable rate.

While top is running you can type h for a list of commands. The space bar will update information instantly.

You can also use top to change a process' priority as we shall see in the next section.

2. Modifying Processes

Stopping processes

The kill command can be used to send signals to processes. There are 63 signals available. The default signal terminates a process and is called SIGTERM with value 15.

kill

Syntax

kill SIGNAL process_PID

Every process can choose whether or not to catch a signal except for the SIGKILL which is dealt with by the kernel. Most daemons redifine the SIGHUP to mean “re-read configuration file”.

Most Common Signals
1 or SIGHUP hangup or disconnect the process 2 or SIGINT same as Ctrl+C interrupt 3 or SIGQUIT quit 9 or SIGKILL kill the process through a kernel call 15 or SIGTERM terminate a process 'nicely'. This is the DEFAULT signal.

One can also stop processes without knowing the process' PID using killall.

killall

Syntax

killall SIGNAL process_NAME

Fig1: Interprocess signaling

Process priority and nice numbers

Nice numbers (NI) alter the CPU priority and are used to balance the CPU load in a multiuser environment. Each process is started with a default nice number of 0. Nice numbers range from 19 [lowest] to -20 [highest].

Only root can decrease the nice number of a process. Since all processes start with a default nice number of zero as a consequence negative nice numbers can only be set by root!

nice numbers and CPU priorities
19 NI PRI users 0 (default) root -20 Pool of processes 0

To modify a process' priority that is already running use renice. To set a process' priority use nice.

Syntax

nice –<NI> <process> renice <+/-NI> -p <PID>

Notice that renice works with PIDs and handles lists of processes at a time. A useful option to renice is the -u option which affects all processes run by a user.

Set nice number 1 for processes 234 and 765:

renice +1 -p 234 765

Set nice number -5 for xclock:

nice --5 xclock

3. Processes and the shell

background and forground processes

After you have started a process from the shell you automatically leave the shell interpreter. You will notice that no commands will respond. The reason for this is that it is possible to run programs in the foreground fg or in the background bg of a shell.

When a program is running in the foreground it is possible to recover the shell prompt but only by interrupting the program for while. The interruption signal is Ctrl Z.

Stopping and starting jobs

A process started from a shell is also called a job. Once the job receives the ^Z signal it is stopped and the shell prompt is recovered. To restart the program in the background simple type: bg.

Example

[mike localhost /bin]$xclock xclock running in forground, shell prompt lost [1]+ Stopped xclock xclock received ^Z signal [mike localhost /bin]$bg shell prompt recovered, issue the bg command [1]+ xclock & xclock is running in the background [mike localhost /bin]$

Notice the [1]+ symbol above. The integer is the process' job number, which it can be referred to as.

The '+' sign indicates the last modified process. A '-' sign would indicate the second last modified process.

One can start a process in the background by appending a & to the command.

xclock& [1] 6213

Listing jobs

The jobs utility lists all running processes started from the current shell. The job number, the job's state (running/stopped), as well as the two last modified processes, will be listed.

Output for jobs
[1]- Stopped xclock [2] Running xman & [3]+ Stopped xload

The job number

One can conveniently stop and start a selection of jobs using the job number. This is achieved with the fg command.

Calling job 2 to the foreground and killing job 1

fg 2 or fg %2 or fg %?xma	kill –9 %1

Avoiding HUP with nohup

Finally there is a program called nohup which acts as a parent process independently from the user’s session. When a user logs off, the system sends a HUP to all processes owned by that process group. For example, to avoid this HUP signal a script called bigbang which attempts to calculate the age of the Universe should be started like this:

nohup bigbang &

4. Exercises and Summary

Review Questions (answers p.150)

Yes or No

1. Running kill against a process will always attempt to kill the given process	_____

2. The commands 'kill $(pidof xeyes ' and 'killall xeyes ' are equivalent	_____

3. A program started with a pending '&' will run in the background	_____

4. A process's nice number is the same as its CPU priority	_____

Glossary

Term	Description
background process	a process started on the shell with $command & Unlike a foreground process the shell doesn't need to wait for the process to terminate before running another command
foreground process	a process started on the shell with $command Once the process is started the shell has to wait for it to terminate before it can run another command
orphaned process	a process whose parent process has terminated. An orphaned process is then 'adopted' by init
PID	a number associated with a process
zombie process	a process that has exited but is still considered by the parent process as present until the next wait() system call. The wait() system call performed by the parent process should refresh the status of the child process as terminated if the process has exited. A zombie process usually doesn't last for long. However due to bugs some zombie processes can last longer taking up system resources even though the process itself has physically exited!

Commands

Command	Description (apropos)
bg	resume a suspended job in the background
Ctrl+Z	keyboard combination used to suspend the current foreground process
fg	send a job in the foreground (making it the current process)
jobs	list of processes started from the current shell
kill	send a specified signal to a process using PIDs
killall	send a specified signal to a process using process names
nice	starts a process with a modified scheduling priority
nohup	nohup(1) – run a command immune to hangups, with output to a non-tty
ps	ps(1) – gives a snapshot of the current processes. If you want a repetitive update of this status, use top
pstree	prints current processes in a hierarchical tree rooted (by default) at init
renice	modified scheduling priority of a running process
top	top(1) – display top CPU processes

Exercises

1. Check the current nice value of your running x-terminal. Change this value using top or renice.

2. What is the equivalent signal of a ^Z sent to a process? (List all signals with kill –l)

3. Which signal is redefined for most daemons and forces the configuration file to be reread?

4. What is the default signal sent to a process, using kill or killall?

5. Which signal is directly handled by the kernel and cannot be redefined?

6. Make sure you log into a virtual terminal (tty1 to tty6) before doing this. We want to run a script that will continue to run once we logout using the nohup parent process.

In the /tmp directory create a file called print-out with the following content:

count=0

while (true) do

echo this is iteration number $count

let count+=1

done

We first do the following (without using nohup) :

cd /tmp
./print-out &
exit

You may not see the command line when typing exit but this should log you out. When you log back in check that print-out is no longer running

ps ux | grep print-out

Next start the command with

nohup /tmp/print-out & exit

Log back in and test these commands

ps ux |grep print-out tail -f ~/nohup.out Ctrl+C killall print-out ps ux|grep print-out tail -f ~/nohup.out

Text Processing

Prerequisites

The Command Line (p.56)

Goals

Effectively manipulate files and data streams to alter the content as required ( e.g sort or format)

Improve command line skills by memorising and understanding simple text tools

Contents

Text Processing	90

1. cat the Swiss Army Knife	91

2. Simple tools	92

3. Manipulating text	94

4. Exercises and Summary	97

1. cat the Swiss Army Knife

cat the editor

The cat utility can be used as a rudimentary text editor.

cat > short-message we are curious to meet penguins in Prague Crtl+D

Notice the use of Ctrl+D. This command is used for ending interactive input.

cat the reader

More commonly cat is used only to flush text to stdout. Most common options are

-n number each line of output

-b number only non-blank output lines

-A show carriage return

Example

cat /etc/resolv.conf

►	search mydomain.org

nameserver 127.0.0.1

tac reads back-to-front

This command is the same as cat except that the text is read from the last line to the first.

tac short-message ► penguins in Prague to meet we are curious

2. Simple tools

using head or tail

The utilities head and tail are often used to analyse logfiles. By default they output 10 lines of text. Here are the main usages.

List 20 first lines of /var/log/messages:

head -n 20 /var/log/messages head -20 /var/log/messages

List 20 last lines of /etc/aliases:

tail -20 /etc/aliases

The tail utility has an added option that allows one to list the end of a text starting at a given line.

List text starting at line 25 in /var/log/messages:

tail +25 /etc/log/messages

Exercise: If a text has 90 lines, how would you use tail and head to list lines 50 to 65? Is there only one way to do this ?

Finally tail can continuously read a file using the -f option. This is most useful when you are expecting a file to be modified in real time.

counting lines, words and bytes

The wc utility counts the number of bytes, words, and lines in files. Several options allow you to control wc's output.

Options for wc

-l	count number of lines
-w	count number of words
-c or -m	count number of bytes or characters

Remarks:

With no argument wc will count what is typed in stdin.

numbering lines

The nl utility has the same output as cat -b.

Number all lines including blanks

nl -ba /etc/lilo.conf

Number only lines with text

nl -bt /etc/lilo.conf

replacing tabs with spaces

The expand command is used to replace TABs with spaces. One can also use unexpand for the reverse operations.

viewing binary files

There are a number of tools available for this. The most common ones are od (octal dump) and hexdump.

splitting files

The split tool can split a file into smaller files using criteria such as size or number of lines. For example we can spilt /etc/passwd into smaller files containing 5 lines each

split -l 5 /etc/passwd

This will create files called xaa, xab, xac, xad ... each file contains at least 5 lines. It is possible to give a more meaningful prefix name for the files (other than 'x') such as 'pass-5.' on the command line

split -l 5 /etc/passwd passwd-5

This has created files identical to the ones above (aa, xab, xac, xad ...) but the names are now passwd-5aa, passwd-5ab, passwd-5ac, passwd-5ad ...

Erasing consecutive duplicate lines

The uniq tool will send to STDOUT only one version of consecutive identical lines. Consider the following example:

uniq > /tmp/UNIQUE

line 1

line 2

line 2

line 3

line 3

line 3

line 1

^D

The file /tmp/UNIQUE has the following content:

cat /tmp/UNIQUE

line 1

line 2

line 3

line 1

NOTICE
From the example above we see that when using uniq non consecutive identical lines are still printed to STDOUT. What is the content of /tmp/UNIQUE if we first send the STDIN through sort (see p.95) as follows:
sort | uniq > /tmp/UNIQUE

3. Manipulating text

The following tools modify text layouts.

choosing fields and characters with cut

The cut utilility can extract a range of characters or fields from each line of a text.

The –c option is used to manipulate characters.

Syntax:

cut –c {range1,range2}

Example

cut –c5-10,15- /etc/password

The example above outputs characters 5 to 10 and 15 to end of line for each line in /etc/password.

One can specify the field delimiter (a space, a commas etc ...) of a file as well as the fields to output. These options are set with the –d and –f flags respectively.

Syntax:

cut -d {delimiter} -f {fields}

Example

cut -d: -f 1,7 --output-delimiter=" " /etc/passwd

This outputs fields 1st and 7th of /etc/passwd delimited with a space. The default output-delimiter is the same as the original input delimiter. The --output-delimiter option allows you to change this.

joining and pasting text

The easiest utility is paste, which concatenates two files next to each other.

Syntax:

paste text1 text2

With join you can further specify which fields you are considering.

Syntax:

join -j1 {field_num} -j2{field_num} text1 text2 or join -1 {field_num} -2{field_num} text1 text2

Text is sent to stdout only if the specified fields match. Comparison is done one line at a time and as soon as no match is made the process is stopped even if more matches exist at the end of the file.

sorting output

By default, sort will arrange a text in alphabetical order. To perform a numerical sort use the -n option.

formatting output with fmt and pr

You can modify the number of characters per line of output using fmt. By default fmt will concatenate lines and output 75 character lines.

fmt options

-w number of characters per line -s split long lines but do not refill -u place one space between each word and two spaces at the end of a sentence

Long files can be paginated to fit a given size of paper with the pr utility. One can control the page length (default is 66 lines) and page width (default 72 characters) as well as the number of columns.

When outputting text to multiple columns each column will be evenly truncated across the defined page width. This means that characters are dropped unless the original text is edited to avoid this.

translating characters

The tr utility translates one set of characters into another.

Example changing uppercase letters into lowercase

tr 'A-B' 'a-b' < file.txt

Replacing delimiters in /etc/passwd:

tr ':' ' ' < /etc/passwd

Notice: tr has only two arguments! The file is not an argument.

4. Exercises and Summary

Review Questions (answers p.150)

Yes or No

1. The commands 'cat FILE ' and 'cat < FILE ' will both display the contents of FILE	_____

2. The command 'last FILE ' will display the 10 last lines of FILE	_____

3. When altering lines from a file using cut those changes are made on the STDOUT only	_____

4. When running uniq against a file consecutive identical lines are deleted in the file	_____

Commands

Command	Description (apropos)
cat	cat(1) – concatenate files and print on the standard output
cut	cut(1) – remove sections from each line of files
expand	expand(1) – convert tabs to spaces
fmt	fmt(1) – simple optimal text formatter
head	head(1) – output the first part of files
join	join(1) – join lines of two files on a common field
nl	nl(1) – number lines of files
od	od(1) – dump files in octal and other formats
paste	paste(1) – merge lines of files
sort	sort(1) – sort lines of text files
split	split(1) – split a file into pieces
tac	tac(1) – concatenate and print files in reverse
tail	tail(1) – output the last part of files
tr	tr(1) – translate or delete characters
unexpand	unexpand(1) – convert spaces to tabs
uniq	uniq(1) – remove duplicate lines from a sorted file
wc	wc(1) – print the number of bytes, words, and lines in files

Exercises

1. Use cat to enter text into a file called message.

cat >> message

line 1

^D

Do the same but use the keyword STOP instead of the predefined eof control (^D).

cat >> message << STOP

line 2

STOP

Next, append text to message using echo.

echo line 3 >> message

2. Create a file called index with two fields REFERENCE and TITLE separated by a space.

e.g	001	Using_Linux

Create a second file pricing with two fields REFERENCE and PRICE separated by a space

e.g	001	9.99

Use join to display the reference, title and prices fields.

3. Using tr replace all colons by semi-colons in /etc/passwd.

Do the same using cut.

4. Use head and tail to list lines 70 to 85 of /var/log/messages.

5. Use the cut utility together with grep and ifconfig to printout only the IP address of the first

network interface eth0.

6. In /tmp make a directory called files

mkdir /tmp/files

Create 50 files in that directory:

#!/bin/bash

count=0

while [ $count -lt 50 ]; do

touch /tmp/files/$count.txt

let count+=1

done

We want to change all the txt extensions to dat extentions. For this we need to type the following on the command line:

for FILES in $(ls *.txt)
do
FILENAME=$(echo $FILES| cut -d. -f1)
mv $FILES $FILENAME.dat
done

Software Installation

Prerequisites

The Command Line (p.56)

Goals

Understand the use of a Makefile when compiling large projects from source

Manipulate source archives effectively and run the appropriate build commands

Fix problems related to shared (or dynamic) libraries

Use the RPM package manager to query, add, remove, update or verify software

Contents

Software Installation	99

1. Introduction	100

2. Static and Shared Libraries	101

3. Source Distribution Installation	105

4. The RedHat Package Manager RPM	108

5. Debian Package Management	113

6. The Alien Tool	117

7. Exercises and Summary	118

1. Introduction

We begin with a short code example. Although we don’t need an advanced understanding of the C language, these examples can help trouble shoot common situations.

The main.c file:

#include<stdlib.h>

int main(){

Hello();

}

The Hello.c file:

#include<stdio.h>

void Hello(){

printf(“Hi ! \n”);

}

Notice that the main.c is incomplete in the sense that the Hello() function is undefined. In the same way Hello.c doesn’t have a “main” declaration. So these files are interdependent. One can however compile object files (.o) which are like non-executable binary files which can be used to ‘build’ an application.

Compiling the object files:

gcc –c main.c gcc –c Hello.c

This will generate two files main.o and Hello.o which can now be used to build the application app.

Compiling app:

gcc –o app main.o Hello.o

The –o option simply specifies a name for the compiled code. If no name is specified the compiled output is called a.out by default.

All these steps can be automated using a Makefile. Here is a minimal Makefile which would compile the app executable.

Makefile

SHELL = /bin/sh

CC = /usr/bin/gcc

app: main.o Hello.o

$(CC) –o app main.o Hello.o

main.o: main.c

$(CC) –c main.c

Hello.o: Hello.c

$(CC) –c Hello.c

2. Static and Shared Libraries

Functions that will often be used are archived as libraries. During compilation these libraries can be linked to the code which uses the library function calls. The library can either be statically or dynamically linked to the code.

The gcc compiler can link libraries in a variety a ways (many options). However by default it will link files that are given on the commandline that don’t have a .c extention (only the .c files are treated as code).

Listing 1: Linking by default

gcc main.c Hello.o

This will produce an a.out executable with the Hello.o object statically linked to it.

Illustration of a statically linked application (a.out):

Hello.o

a.out

● Static libraries

Static libraries are archived .o files. These archives are created with the ar tool and have a .a extention.

Listing2: adding an object file to an archive:

ar rcs libfoo.a file1.o file2.o

● Dynamic/Shared Libraries

A shared library is a library that will be loaded by the program when it is executed. One also says that the library is dynamically loaded.

Listing 3: Creating a shared library:

gcc –c –fPIC Hello.c creates the object file gcc –shared –W1,soname,libfoo.so.1 –o libfoo.so.1.0 Hello.o

The –fPIC flag enables the Position Independent Code generation.

Listing4: Compiling with a shared library:

gcc main.c libfoo.so.1.0

This will produce an a.out executable. However if you try to run this it will complain with the error message listed below.

Illustration of a dynamically linked application (a.out):

libfoo.so

a.out

The process of attaching a dynamic library at run-time is called linking and is handled by the ld.so library. How does the linker know where to find libfoo.so?

Shared library not found error:

./a.out: error while loading shared libraries: libfoo.so.1.0: cannot open shared object file: No such file or directory

This error illustrates the case where the linker could not find the dynamic library libfoo.so.1.0. In the next section we will see what can be done to fix this problem.

● Shared Library naming and dynamic loading

We will use the above example to understand how Linux libraries are maintained.

Figure 1: The Shared Library Names

To find out which shared libraries an executable needs at execution time the ldd tool is used.

Example:

ldd a.out ► libfoo.so.1.0 => not found libc.so.6 => /lib/libc.so.6 (0x40028000) /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)

Notice that libfoo.so.1.0 is not found. This is because the a.out needs to dynamically load this library and the dynamic linker ld.so is not aware of this new library.

In fact the linker uses a database called the ldcache containing entries of the form:

soname =>/path/to/library

The content of the ld-cache can be viewed with the following command:

ldconfig -p
► libaudiofile.so.0 (libc6) => /usr/lib/libaudiofile.so.0
libaudiofile.so (libc6) => /usr/lib/libaudiofile.so
libaudio.so.2 (libc6) => /usr/X11R6/lib/libaudio.so.2
libattr.so (libc6) => /usr/lib/libattr.so ..........

The ld-cache is generated at boot time by the same ldconfig tool. By default ldconfig will scan the directories /lib and /usr/lib to build the ld-cache.

If libraries are installed in different locations (e.g /usr/local/lib, /opt/lib or /usr/X11R6/lib) these directories need to be listed in /etc/ld.so.conf allowing ldconfig to take these directories into consideration when building the cache.

What happens when an application is started?

The application will ask the linker for the dynamic libraries it needs using a soname, the linker will then query the ld-cache and associate this name with the full path to the actual library. Once the full path is known the linker can link the library to the application.

What happens if the ld-cache doesn't contain the full path to the library?

In general the application will fail to start and will print an error message saying “ cannot open shared object file: No such file or directory “. But one can also define a global variable called LD_LIBRARY_PATH and assign to this variable the name of the directory containing the library.

Knowing this we can now fix the problem with our application above using one of the tw0 methods below:

1. If the binary needs to be temporary tested define the LD_LIBRARY_PATH variable as follows:

export LD_LIBRARY_PATH=$(pwd)

2. If you are root and would like the library to be available for all then copy the libfoo.so.1.0 file to /usr/local/lib/ and run ldconfig to update the ld cache.

The GNU specification advises libraries to be stored in /usr/local/lib. These guidelines are followed by developers and most tarballed code will install libraries in that directory and the binaries in /usr/local/bin. Installing and removing this code from the system would be done by ¨make install¨ and ¨make uninstall¨.

The FHS (Filesystem Hierarchy Standard) recommends libraries be kept in /usr/lib/ and associated binaries in /usr/bin/. This convention standard is adhered to by Linux distributions. In effect mature and stable code is stored in /usr/ rather than /usr/local/ and the two standards do not lead to any contradictions. Installing and removing this code code would be done using the rpm command.

NOTICE
With certain distributions the /usr/local/lib/ directory is not scanned by ldconfig. It is simply a matter of adding this directory to /etc/ld.so.conf and ... reboot?

3. Source Distribution Installation

Open source projects are often distributed as tarballs (i.e compressed tarred archives). Many development environments (glade, kdevelop…) generate the files that help facilitate compiling and installation of a project.

Uncompressed Archives

Uncompressed archives have a .tar extension. For example if a project has been developed in a directory called my-projetc-v.1/ then the following command would archive this directory with all its files and subdirectories:

tar c my-project-v.1/ > my-project-v.1.tar

or

tar cf my-project-v.1.tar my-project-v.1/

Since most projects are very large and are available for download from the Internet they are rarely uncompressed.

Compression

The three compression tools commonly used are compress (old), gzip and bzip2. Unlike the windows zip these compressions can only be applied to files. But since an archive is a file that contains all the data needed to recover directories, these compressions are suitable for archives. A compressed archive is then called a tarball.

compression tool	de-compression tool	cat decompression	file extension
compress	uncompress	zcat	.Z
gzip	gunzip	zcat	.gz
bzip2	bunzip2	bzcat	.bz2

Examples

compress -v FILE1
FILE1: -- replaced with FILE1.Z Compression: 40.29%
gzip -v FILE2
FILE2: 53.4% -- replaced with FILE2.gz
bzip2 -v FILE3
FILE3: 2.326:1, 3.439 bits/byte, 57.01% saved, 605504 in, 260320 out.

NOTICE
1. When compressing a file, the original file name is appended a .Z,.gz or .bz2 2. Compression tools listed above only work on files and not on directories 3. Only one file at a time can be compressed (no wild cards!)

The zcat and bzcat tools can be used to decompress files, however the decompressed file will be sent to STDOUT so it is necessary to use a file redirection:

zcat FILE1.Z > FILE1

Archives and Compression

compression tool	tar switch	archive extension
compress	Z	.tar.Z or .tgZ
gzip	z	.tar.gz or .tgz
bzip2	j	.tar.bz2

The table above introduces the tar options Z,z and j which call the appropriate compression tools when needed.

The next two examples are equivalent:

tar cf my-project-v.1.tar my-project-v.1/ bzip2 my-project-v.1.tar

tar cjf my-project-v.1.tar.bz2 my-project-v.1/

Working with tarballs

We know how to create archives. All we need is an overview of the main tar switches.

tar operations	Create	Extract	Test
minimal switches	c or cf	xf	tf
optional switches	v,Z,z,j	v,Z,z,j	v,Z,z,j

Examples (extractions)

tar xvjf myproject-v.1.tar.bz2
tar xzf some-other-project-v.2.0.tar.gz

Examples (tests)

tar tjf myproject-v.1.tar.bz2
tar tzf some-other-project-v.2.0.tar.gz

Alternative Examples (using zcat and bzcat)

bzcat myproject-v.1.tar.bz2 | tar xf -
zcat some-other-project-v.2.0.tar.gz | tar tf -

Common Files

Once a project has been extracted you can expect to find the following files:

configure: This is a script which determines what architecture is being used. It also checks that the required compiler, libraries an headers are present. This information is then stored in files called Makefile

The safest way to run the script is to use ‘./configure’.

You can also decide where the project will be installed using the –-prefix option. The default installation directory for most projects is /usr/local. If you want to install the compiled project in your home directory you should type:

./configure –prefix=$HOME

Makefile: This acts like a configuration file for the make utility. The main information provided is:

- The name of the compiler and compiling options

- The path to the shared libraries and header files

- Mapping between code files (.c) and object files (.o)

Compiling the project

If the files above are present then there is a good chance that you will successfully ‘port’ the program to your computer. Here are the routine steps:

./configure make make install

It is strongly recommended to run ./configure and make as a non root user.

make install must be run as root only if the installation directories are write protected (/usr/ or /usr/local).

There are many options to the ./configure script. To customise your installation you could type

./configure –-help

4. The RedHat Package Manager RPM

Most Linux distributions manage software using some form of package management to perform tasks such as installations, updates and queries. The most popular package types are Debian and RPM. We only cover RPM in this manual.

The Functions of a Package Manager

Package naming

There is no strict convention but most rpm package names are formed as follows:

name-version-release.architecture.rpm

The architecture name can either indicate which computer architecture the enclosed binaries are made for (e.g i386, ppc, ia64, noarch) or it can indicate that the package contains the source code (src).

Major and minor modes

Some short name options are similar but perform different actions depending on their position on the command line. A distinction is made between the first option and other options.

The first option given to rpm is in major mode. For example in rpm -iv A.rpm the option 'i' is a major option and will cause package A to be installed.

Similarly an option that is not in first position is in minor mode. For example in rpm -qpi A.rpm the option 'i' is a minor mode and will get information from the package A such as the author and the licence type.

These are the major mode options for rpm.

Short	Long	Description
-i	–install	Installs the package
-U	–update	Updates or installs a package
-F	--freshen	Updates only installed package
-V	--verify	file size, MD5, permissions, type ...
-q	--query	Queries installed/uninstalled packages, and files
-e	–erase	Uninstall package

These are the minor mode options for rpm.

Short	Description
a	applies to all installed packages
c	together with q lists configuration files
d	together with q lists documentation files
f	together with q queries which package installed a given file
h	adds hashes while processing
i	together with q lists information about a package
l	together with q lists all files and directories in a package
p	together with q specifies that the query is performed on the package file
v	verbose

Query modes

Three query types: uninstalled packages, installed packages and files

Query Type	Option
Package file	-qp
Installed package	-q
File	-qf

An extra option will allow you to get information on all installed files –l, documentation –d configuration files –c, etc ...

We consider for example the package routed-0.17.i386.rpm. We can query this package and list its contents before installation with the l option as follows:

rpm –qpl routed-0.17.i386.rpm

Once this package is install we can query the installed package with:

rpm –ql routed-0.17 or rpm –ql routed

Finally if we want to find out which package installed the file /usr/sbin/routed the rpm database can be queried with:

rpm –qf /usr/sbin/routed

Special Options

--nodeps	install a package regardless of dependencies

--force	force an upgrade

--test	doesn’t actually install or upgrade, just prints to stdout

--requires PACKAGE	together with q lists capabilities required by a package

--whatrequires	CAPABILITY	together with q lists packages which require the capability

Package Signatures

You can check the signature of each package that is distributed as part of a project. For example to load the keys of all the developers involved with the Fedora project do the following (just once):

rpm –-import /usr/share/rhn/RPM-GPG-KEY-fedora

You can now download any package from an FTP site which mirrors the project's RPMs. For example we downloaded zlib-1.2.1.1-2.1.i386.rpm from ftp.mirror.ac.uk in the Fedora subdirectory. We next check the authenticity of the file:

rpm --checksig /home/adrian/zlib-1.2.1.1-2.1.i386.rpm
/home/adrian/zlib-1.2.1.1-2.1.i386.rpm: (sha1) dsa sha1 md5 gpg OK

Package Integrity

The next command checks the integrity of the package bash:

rpm –V bash

This returns nothing. We next do the following as user root:

chown bin /bin/bash chmod 775 /bin/bash

If we check the integrity of bash again this time we get:

rpm –V bash .M...U.. /bin/bash

The package manager has compared the current status of all files which are part of the bash package with the known original state of these files stored in a database. The changes made to /bin/bash have been identified.

It is possible to verify the integrity of all packages installed on the system by adding the 'a' (--all) option after 'V' (--verify)

The –verify option performs a number of tests on each file; when a test is positive a number of characters (listed below) are used to identify the errors:

Returned character	Error description
.	the test was successful
?	the test couldn't be performed
S	file size has changed
M	permission mode or file type has changed
5	the file's MD5 sum has changed
D	device major/minor number miss-match
L	broken symbolic link
U	the user owner of the file has changed
G	the group owner of the file has changed
T	the mtime (modified time) has changed

Going Further: Building RPM packages (not for LPI exam purpose)

NOTICE:
This is additional information, this paragraph is not an LPI 101 objective. When doing this section you may encounter problems with the –-rebuild option, this is due to the fact that the new versions of RPM use rpmbuild instead of rpm when rebuilding packages.

The source code for many RPM packages is also available as an RPM package and will be used to build a binary package. The naming convention is:

name-version-release.src.rpm

These packages contain at least two files, the tarball with the code and a spec file. The spec file contains instructions to patch, compile and build the RPM package. If the code needs to be patched before compilation then the patches are included in the source package.

There are three different ways to build a RPM package. We will assume that we have a package called name-version-release.src.rpm.

For these methods to work you first need to install the rpm-build package

Method 1:

Install the RPM source package with:

rpm –ivh name-version-release.src.rpm

This will copy files to the following directories:

/usr/src/redhat/SPECS

/usr/src/redhat/SOURCES

In the /usr/src/redhat/SPECS directory there is now a file called name.spec (where ‘name’ is the name of the package). To start building the compiled package, that is name-version-release.i386.rpm, we type in the following command:

rpm –ba name.spec

This will start a series of scripts. The tarball in /usr/src/redhat/SOURCES will be unpacked in /usr/src/redhat/BUILD.

If the compilation succeeds then the built binary package will be saved in /usr/src/redhat/RPMS/. There are different subdirectories corresponding to various CPU models/generations. If the compilation didn’t involve specific features from these chips then the package will be saved in the noarch directory.

Method 2:

This method triggers the same chain of events as the previous one but is started with the following single command:

rpm –-rebuild name-version-release.src.rpm

Method 3:

In some cases developers will distribute a tarball together with a spec file. If the tarball is called name-version-release.tar.gz you can search for a .spec file with the following:

tar tzvf name-version-release.tar.gz | grep .spec

If the tarball has a spec file then you can build an RPM package by typing:

rpm –bt name-version-release.tar.gz

5. Debian Package Management

Systems using Debian based variants of Linux don't use the rpm package management system, but rather the Debian Package Management system. The Debian system is more rigorous and configurable than the rpm system, but for historical reasons is less widely used.

The approach used by the the Debian system is very similar to that used by the rpm system. The equivalent command to 'rpm' in a Debian system is 'dpkg'.

Package Naming

Similarly to RPM-based system, Debian packages come in files whose names are formed as follows:

name_version-release_architecture.deb

The release number indicates which Debian release of the version of the software the package contains, while the architecture name specifies the computer architecture (i386, sparc, all).

dpkg

dpkg is a medium-level tool to install, build, remove and manage Debian packages. Other front-end packages are more commonly used to contol dpkg, including the apt tools and others such as dselect. dpkg itself is controlled via command line parameters, which consist of an action and zero or more options. The action parameter tells dpkg what to do and options control the behaviour of the action in some way.

dpkg maintains some usable information about available packages. The information is divided in three classes: states, selection states and flags.

Package States

State	Description
installed	The package is unpacked and configured OK.
half-installed	The installation of the package has been started, but not completed for some reason.
not-installed	The package is not installed on your system.
unpacked	The package is unpacked, but not configured.
half-configured	The package is unpacked and configuration has been started, but not yet completed for some reason.
config-files	Only the configuration files of the package exist on the system.

Package Flags

Flag	Description
hold	A package marked to be on hold is not handled by dpkg, unless forced to do that with option –force-hold.
reinst-required	A package marked reinst-required is broken and requires reinstallation. These packages cannot be removed, unless forced with option --force-reinstreq.

Actions

The heart of dpkg operation is the command line parameters specifying the action which should be performed. While there are a large number of these, the following table summarises the main actions you are likely to require on any regular basis.

Action	Description
-l	Prints a list of the packages installed on the system, or matching a pattern if any is given. The first three characters on each line show the state, selection state, and flags of the package
-s	Shows the status and information about particular installed package(s)
-I	Show information about a package in a .deb file
-L	List the files included in a package
-S	Show the package which includes the file specified
-i	Install (or upgrade) and configure a package from a .deb file
--unpack	Unpack (only) a package in a .deb file
--configure	Configure an unpacked package. With -a (or --pending) configures all packages requiring configuration
-r	Remove a package (but leave its configuration files)
-P	Purge – remove a package along with its configuration files
--get-selections	Get a list of package selections from a system (to stdout)
--set-selections	Set the list of package selections for a system (from stdin)

Options

All options can be specified both on the commandline and in the dpkg configuration file /etc/dpkg/dpkg.cfg. Each line in the configuration file is either an option (exactly the same as the commandline option but without leading dashes) or a comment (if it starts with a #).

Option	Description
-force-thing	Forces dpkg to perform an action which it would normally not take (for example, to ignore dependency information - --force-depends, or to downgrade a package with –force-downgrade)
--refuse-thing	Refuse to do something which dpkg would normally automatically do
--ignore-depends	Ignore dependency checking for a package
--no-act	Show what dpkg would do, but don't do it (also: --simulate)
-R	Recurse through directories (using with -i or --unpack)

Files

dpkg uses a number of files in its operation, including /etc/dpkg/dpkg.cfg which contains default configuration settings.

Lists of available packages along with their statuses are held in the files

/var/lib/dpkg/available and /var/lib/dpkg/status.

A .deb file, along with the files making up a packages programs, libraries and configuration, will also include a number of control files which allow the execution of scripts before and after installation and removal, along with lists of files and configuration files. These can be found in the /var/lib/dpkg/info directory once the packages are installed.

Use of dpkg

To install a package from a .deb file, you could use dpkg as follows:

dpkg –i hello_2.1.1-4_i386.deb OR dpkg --unpack hello_2.1.1-4_i386.deb dpkg --configure hello

To remove the hello package along with its configuration, you could use:

dpkg –P hello

While:

dpkg –r hello

would remove only the package, leaving its configuration files installed.

The get a list of all the packages installed on the system, use the command:

dpkg –l

Note that when dealing with a package file, the filename is given, while when dealing with an installed package, the package name only is given.
APT

The dpkg tool is fine for installing individual packages with no dependencies, but when installing a number of packages which may have dependencies, the APT tool is generally used instead.

APT is one of the strengths of dpkg, and provides an easy way of installing and updating a system. It is controlled by two files:

File	Description
/etc/apt/apt.conf	Contains general configuration options for APT, such as which release of Debian to install, whether/which proxy settings to use, etc
/etc/apt/sources	Lists sources of Debian files, which may be on CDs, or on the network

In general, to use APT you must first configure the sources it is to used. This can be done (if you are using CDs) by using the command:

apt-setup

which asks the user to choose which mirror to download from, and tests it, or if you are using CDs, using:

apt-cdrom

which allows individual CDROMs to be scanned for packages.

Once APT knows where the Debian packages are located, two command line tools are used for package management: apt-cache and apt-get.

apt-cache

apt-cache allows manipulation of the APT package cache (which is stored in files in /var/cache/apt). An action normally follows apt-cache on the command line, and common options include:

Action	Description
search	Search all the available package descriptions for the string given, and print a short description of the matching package
show	Shows a full description of the package specified

apt-get

While apt-cache is useful for finding out information about available packages, apt-get allows updating of package information, retrieval, installation and removal of packages, and even upgrading of an entire Debian distribution. apt-get expects an action to be provided on the command line, and the most common are listed below:

Action	Description
update	Update the list of packages from the sources in /etc/apt/sources.list
install package	Install the package(s) specified, along with any dependencies
upgrade	Upgrade any packages which have newer versions available
dist-upgrade	Upgrade entire distribution to the latest release (best to read the release notes first!)
remove	Remove the package(s) specified

Use of APT

The two main uses of APT are for updating the system (for example if security-related updates have become available). This is normally done using the two commands:

apt-get update apt-get upgrade

The other main use of APT is to install required packages. This normally involves the following commands:

apt-get update #update list of packages apt-cache search frob #find packages relating to frobbing apt-cache show frobnicate #show information regarding a particular package apt-get install frobnicate #install frobnicate package and its dependencies

6. The Alien Tool

The alien tool will change Debian packages into RedHat ones and vice versa. One can download it at: http://kitenet.net/programs/

Convert a debian package to an rpm:

alien –to-rpm package.deb

Convert an rpm package to debian:

alien –to-debian package.rpm

7. Exercises and Summary

Review Questions (answers p.150)

Yes or No

1. When building a project from source one has to compile sections of the code in the

correct order using gcc on the command line	_____

2. The program make will only build a project if it is started in a directory containing

the appropriate Makefile	_____

3. Pre-compiled binary packages and source code packages are two types of RPM

packages	_____

4. Once shared libraries have been installed from source it is recommended to run ldconfig	_____

5. The ldconfig tool is used to update the ld-cache	_____

6. Program installed from source can be queried using a package manager	_____

7. The APT tools can install packages and resolve all dependencies	_____

Glossary

Term	Description
build	term used when compiling a project from source, usually started by typing make
compile	translate programming instructions written in a high-level language into machine readable code. The output of a compilation is called the object code
dynamic library shared library static library	a library that can be loaded at the same time as the execution of a program a library intended to be used by more than one executable. Shared libraries are often dynamic libraries and have a .so extension (shared object) a library that is copied into the executable during the compilation. Static libraries have .a extensions (archive)
high-level language	a programming language readable by humans used to write source code
linker	1. program used during the compilation process to assemble objects generated by the compiler into an executable – see ld(1) 2. program that dynamically loads shared libraries needed by an executable at runtime – see ld.so(8)
object code	the output of a compilation. Object code is either an executable or may be linked to another object code to form an executable
source code	programming instructions written in a high-level language that need to be compiled with a compiler or interpreted with an interpreter
tarball	a compressed tar archive

Files

File	Description
/etc/ld.so.conf	configuration file for ldconfig
Makefile	file read by the make utility when building a project
/etc/rpmrc	used by rpm and rpmbuild (see LPI 201), this file contains information such as the system's architecture or the path to macros and utilities used when handling packages. This file is often located in the /usr/lib/rpm/ directory
/usr/lib/rpm/	directory containing all the macros needed when handling packages
/var/lib/rpm/	directory where databases for the package manager (RPM) are kept

Commands

Command	Description
alien	alien(1) – Convert or install an alien binary package. It converts between Red Hat rpm, Debian deb, Stampede slp, Slackware tgz, and Solaris pkg file formats. If you want to use a package from another Linux distribution than the one installed on your system you can use alien to convert it to your preferred package format and install it
APT tools	Tools used to perform advanced operations on Debian packages located on a CD or a server
configure	script often included with a project source code used to create makefiles. It attempts to determine information such as the system's CPU type or installed components needed to build the project(compiler, header files or libraries).
dpkg	tool used to manipulate packages in the DEBIAN format
LD_LIBRARY_PATH	environment variable containing the search path to shared libraries used by the linker (ld.so)
ldconfig	program that builds the 'ldcache' used by the linker to find shared libraries, with the -p flag it will print the current content of the cache
ldd	ldd(1) – prints the shared libraries required by each program or shared library specified on the command line
make	info make – The `make' utility automatically determines which pieces of a large program need to be recompiled, and issues commands to recompile them.
rpm	tool used to manipulate packages in the RPM format

Exercises

In the following examples download a source RPM file (e.g. bash-2.05-8.src.rpm for RedHat 7.2) from www.rpmfind.net.

1. Installing as a tarball.

- Extract the contents of the RPM package without compiling anything with:

rpm –ivh bash-2.05-8.src.rpm

- In the /usr/src/redhat/SOURCES directory, unpack the tarball with:

tar xvzf bash-2.05-8.tar.gz

- Optional (recommended!): The patches can be applied. Depending on which directory you are in the syntax will vary.

From /usr/src/redhat/SOURCES:

patch –p0 –b < file.patch

From /usr/src/redhat/SOURCES/bash-2.05-8

patch –p1 –b < file.patch

- We will choose to install the files in a temporary root directory, for example /tmp/project-test/. On a production system the usual location should be /usr/local. We create this directory:

mkdir /tmp/project-test

- Finally follow the usual compilation steps.

./configure –prefix=/tmp/project-test

make

make install

You can now list the content on /tmp/project-test.

2. (Going further – not required for LPI101) We next rebuild the project into an RPM package.

rpm –-rebuild package.src.rpm

The compiled binary package should be in /usr/src/redhat/RPMS

- Check the package’s contents with the –qpl option

- Install the package(s), and run queries on the installed package

- Uninstall the package

3. Configure /etc/apt/sources using apt-setup. Use the APT tools and dpkg to query/install/update available packages.

Advanced Text Manipulation

Prerequisites

The Command Line (p.56)

Text Processing (p.91)

Goals

Distinguish expressions used for file globbing (metacharacters) and regular expressions

Use the grep tools effectively

Understand simple sed commands

Contents

Advanced Text Manipulation	121

1. Regular Expressions	122

2. The grep family	122

3. Working with grep	123

4. egrep and fgrep	123

5. The Stream Editor - sed	124

6. Exercises and Summary	126

Overview

Finding a word or multiple words in a text is achieved using grep, fgrep or egrep. The keywords used during a search are a combination of letters called regular expressions. Regular expressions are recognised by many other applications such as sed, and vi.

1. Regular Expressions

Traditional Regular Expressions (regex)

A regular expression is a sequence of characters (or atoms) used to match a pattern. Characters are either constants (treated literally) or metacharacters.

Table1: Main metacharacters

Characters	Search Match
\<KEY	Words beginning with ‘KEY’
WORD\>	Words ending with ‘WORD’
^	Beginning of a line
$	End of a line
[ Range ]	Range of ASCII characters enclosed
[^c ]	Not the character ‘c’
\[	Interpret character ‘[‘ literally
“ca*t”	Strings containing ‘c’ followed by no 'a' or any number of the letter 'a' followed by a 't'
“.”	Match any single character

Extended regex: The main eregex’s are: +,?,() and |

Table2: List of main eregex

Characters	Search Match
"A1|A2|A3"	Strings containing ‘A1’ or ‘A2’ or ‘A3’
"ca+t"	Strings containing a 'ca' followed by any number of the letter 'a' followed by a 't'
"ca?t"	Strings containing ‘c’ followed by no 'a' or exactly one 'a' followed by a 't'
"ca*t"	Strings containing ‘c’ followed by no 'a' or any number of the letter 'a' followed by a 't'

2. The grep family

basic grep

The grep utility supports regular expressions regex such as those listed in Table1.

egrep

The egrep tool supports extended regular expressions eregex such as those listed in Table2.

fgrep

Fgrep stands for fast grep and fgrep interprets strings literally (no regex or eregex support)

3. Working with grep

Syntax for grep:

grep PATTERN FILE

grep	Main Options
-c	count the number of lines matching PATTERN
-f	obtain PATTERN from a file
-i	ignore case sensitivity
-n	indicate the input file's line number
-v	output all line except those containing PATTERN
-w	match exact PATTERN

For example list all non blank lines in /etc/lilo.conf:

grep –v “^$” /etc/lilo.conf

4. egrep and fgrep

The fgrep utility does not recognise the special meaning of the regular expressions. For example

fgrep ‘cat*’ FILE

will only match words containing ‘cat*’. The main improvement came from fgrep’s ability to search from a list of keywords entered line by line in a file, say LIST. The syntax would be

fgrep –f LIST FILE

The egrep utility will handle any modern regular expressions. It can also search for several keywords if they are entered at the commandline, separated by pipes. For example;

egrep “linux|^image” /etc/lilo.conf

5. The Stream Editor - sed

At this point the stream editor makes its appearance! It is an old type of tool and originally the only one available under UNIX to manipulate text.

The sed utility is most often used to search and replace patterns in text. It supports most regular expressions.

5.1 Beginning sed

Syntax for sed

sed [options] ´command’ [INPUTFILE]

The input file is optional since sed also works on file redirections and pipes.

Here are a few examples assuming we are working on a file called MODIF.

Delete all commented lines:

sed ‘/^#/ d ’ MODIF

Notice that the search pattern is between the double slashs //.

Substitute /dev/hda1 by /dev/sdb3:

sed ‘s/\/dev\/hda1/\/dev\/sdb3/g’ MODIF

The s in the command stands for ‘substitute’. The g stands for “globally” and forces the substitution to take place throughout each line.

If the line contains the keyword KEY then substitute ‘:’ with ‘;’ globally:

sed ‘ /KEY/ s/:/;/g’ MODIF

5.2 More Advanced sed

You can issue several commands each starting with –e at the command line. For example, (1) delete all blanks then (2) substitute ‘OLD’ by ‘NEW’ in the file MODIF

sed –e ‘/^$/ d’ -e ‘s/OLD/NEW/g’ MODIF

These commands can also be written to a file, say COMMANDS. Then each line is interpreted as a new command to execute (no quotes are needed).

An example COMMANDS file
1 s/old/new/
/keyword/ s/old/new/g
23,25 d

The syntax to use this COMMANDS file is:

sed -f COMMANDS MODIF

This is much more compact than a very long commandline !

Summary of options for sed

Commandline flags
-e Execute the following command
-f Read commands from a file
-n Do not printout unedited lines

sed commands
d Delete an entire line
r Read a file and append to output
s Substitute
w Write output to a file

6. Exercises and Summary

Review Questions (answers p.151)

Yes or No

1. The extended regular expression 'nucle?ar' will match nuclear and nuclar	____

2. The regular expression 'baza*r' will match bazaar and bazar but not bazor	____

3. The extended regular expression 'nucle+ar' will only match nuclear	____

4. The regular expression 'baza*' will match bazaar, bazar and bazor	____

Commands

Command	Description or apropos
egrep	print lines containing matching patterns using extended regular expressions
fgrep	print lines containing matching patterns using literal stings
grep	print lines containing matching patterns using regular expressions
sed	sed(1) – stream editor is used to perform basic text transformations on an input stream (a file or input from a pipeline)

Exercises

1. Create a new file called FILE containing the lines:

Using grep,

fgrep and

egrep

to grep for 99% of the cats

% these are two

% commented lines

- Use grep to output only uncommented lines.

- Find all lines containing ‘grep’ exactly. (Not ‘egrep’ nor ‘fgrep’.Use -w to match the word)

- Find lines containing words starting with an ‘a’

2. Regular expressions. Append the following lines to the previous file:

ct

cat

caats

caaatss

ca+t

ca*t

ca?t

crate

carts

- Investigate the outcome of the following using grep, egrep and fgrep:

grep 'ca+t' FILE

grep 'ca?t' FILE

grep 'ca.t' FILE

grep 'caa*t' FILE

grep 'ca*r.' FILE

3. Use sed to do the following changes in FILE

(use a COMMAND file, then do everything on the commandline)

- in the first line substitute ‘grep,’ with ‘soap’

- delete ‘fgrep’ in the second line

- substitute ‘egrep’ with ‘ water’

- in the fourth line replace ‘grep for’ with 'wash'

Save the result to a file using the w option

Using vi

Prerequisites	none

Goals

Understand the three operating modes of vi

Introduce most common editing commands

Recognise the use of regular expressions and sed-like commands

Contents

Using vi	128

1. vi Modes	129

2. Text Items	129

3. Inserting Text	130

4. Cut and Paste	130

5. Copy Paste	131

6. Search and Replace	131

7. Undo and Redo	132

8. Running a Shell Command	132

9. Save and Quit	132

10. Exercises and Summary	133

In most Linux distributions vi is the text editor of choice. It is considered an essential admin tool such as grep or cat and is found therefore in the /bin directory.

1. vi Modes

In order to perform complex operations such as copy/paste vi can operate in different modes.

● Command mode

This is the editing and navigation mode. Commands are often just a letter. For example use j to jump to the next line.

As a rule of thumb if you want to perform an operation several times you can precede the command by a number. For example 10j will jump 10 lines.

In some situations the arrow keys on the keyboard are not mapped properly, it is still possible to navigate using the commands h j k l with the following effect:

h	j	k	l

● Last Line (or column) Mode

You enter this mode from the command mode by typing a colon. The column will appear at the bottom left corner of the screen. In this mode you can perform a simple search operation, save, quit or run a shell command.

● Insert Mode

The easiest way to enter this mode while in command mode is to use i or a. This mode is the most intuitive and is mainly used to interactively enter text into a document.

 The Esc key will exit the insert mode and return to command mode

2. Text Items

Items such as words and paragraphs are defined in command mode to allow editing commands to be applied to text documents without using a mouse.

Word, sentences and paragraphs

e resp. b	Move to the end/begining of the current word
( resp. )	Move to the begining/end of the current sentence
{ resp.)	Move to the begining/end of the current paragraph
w	Similar to e but includes the space after the word

Beginning and End

^	Beginning of line
$	End of line
1G	Beginning of file
G	End of file

All these text items can be used to navigate through the text one word (w) or paragraph (})at a time, go to the beginning of a line (^) the end of the file (G) etc. One can also use these text items to execute commands such as deleting and copying.

3. Inserting Text

When in command mode typing i will allow you to enter text in the document interactively. As with all other features in vi there are many other ways of doing this. The table below lists all possible inserting modes.

Insert commands

a	Append text with cursor on the last letter of the line
A	Append text with cursor after last letter at the end of the line
i	Insert text at the current position
o	Insert text on a new line below
O	Insert text on a new line above
s	Delete the current letter and insert
S	Delete current line and insert

A very useful option when modifying a document is to delete a section of text you wish to replace just before entering insert mode. This is done by the change c command. As the other commands in this section c will put you into INSERT mode but you can specify which portion of the text needs to be deleted before. For example:

c$

will delete all the text from the current cursor position to the end of the line.

Another command used to replace a single character (nothing else!) is r. First choose which character needs to be replaced and put the cursor on this character. Next press r followed by a new character. The new character will replace the old one. This command will leave the editor in COMMAND and not INSERT mode!

4. Cut and Paste

If you want to delete a single character while in command mode you would use x and dd would delete the current line. One can then paste the deleted item with the command p.

Remark: Nearly all vi commands can be repeated by specifying a number in front of the command. You can also apply the command to a text item (such as word., sentence, paragraph ...) by placing the entity after the command.

Examples:

Delete a word:

dw

Delete text from here to the end of the current line

d$

Delete text from here to the end of the current paragraph

d}

One can simultaneously delete an item and switch to insert mode with the c command. As usual you can use this command together with a text item such as w or {.

5. Copy Paste

The copy action in vi is the command y (for yank, the letter c was already taken for change), and the paste action is still p.

If an entire line is yanked the pasted text will be inserted on the next line below the cursor.

The text selection is made with the familiar text items w, l, }, $ etc ... There are a few exceptions such as the last example.

Examples:

Copy the text from here to the end of the current line

y$

Copy the entire current line

yy

Copy 3 lines

3yy

 The latest deleted item is always buffered and can be pasted with the p command. This is equivalent to

a cut-and-paste operation.

6. Search and Replace

Since searching involves pattern matching we find ourselves once again dealing with regular expressions (regex). As many UNIX text manipulation tools such as grep or sed, vi recognises regular expressions too.

To perform a search one must be in COMMAND mode. The / (forward slash) command searches forward and the ? command searches backwards.

One can also perform search and replace operations. The syntax is similar to sed.

Example:

Downward search for words beginning with ‘comp’ in all the text

/\<comp

Upward search for lines starting with the letter z

?^z

Search in the whole text for the keyword ‘VAR’ and replace it by ‘var’

:% s/VAR/var

7. Undo and Redo

At this stage is is worth mentioning that one can always undo changes! This must be done in COMMAND mode with the u command (works as long as one hasn’t yet saved the file). The redo command is ^R.

8. Running a Shell Command

While in LASTLINE mode everything following an exclamation mark ! is interpreted as a shell command.

For example while editing lilo.conf or grub.conf you may need to find out the name of the root device. This can be done with:

:!df /

9. Save and Quit

The command for saving is :w. By default the complete document is saved. In some case vi will refuse to save changes made to a document because of insufficient rights. In such cases ione can attempt to force a write with :w!

One can also specify an alternative name for the file. Portions of the text can be saved to another file while other files can be read and pasted in the current document. Here are the examples which illustrate this.

Examples:

Save the current document as ‘newfile’

:w newfile

Save lines 15 to 24 in a file called ‘extract’

:w 15,24 extract

Read from file ‘extract’. The text will be pasted at the cursor

:r extract

Warning: In the column mode context we have the following

.	is the current line

$	is the end of the document

The following are different ways available to quit vi:

:wq	save and quit

:q!	quit but do not save changes

:x	exit and save when changes exist

:quit	same as :q

:exit or :e	same as :x

ZZ	same as :x

10. Exercises and Summary

Review Questions (answers p.151)

Yes or No

1. The command 'l' (lower case L) will place the cursor one position to the left	_____

2. The command 3dd will delete three lines	_____

3. The command 3wd will delete three words	_____

4. The command :qw will write and exit	_____

Commands

vi action	Description
^,$	beginning and end of line
1G,G	beginning and end of document
b,e	beginning and end of word
(,)	beginning and end of sentence
{,}	beginning and end of paragraph
w,W	word and word including hyphens and punctuations
h,j,k,l	left, up, down, right navigation commands
:!	call a shell command
:quit,:q	quit
:quit!,:q!	force quit, discard changes
:wq	write and quit
:exit,:x,:e,ZZ	exit (saves changes if needed)
/,?	search forwards or backwards
a,A,i,o,O,s,S	start insert mode
c	start insert mode while changing an item
r	replace a single character in command mode
d,dd	delete an item or delete entire line
x	delete a single character
y,yy	yank item or entire line
p	paste content of buffer
u,^R	undo, redo

Exercises

As root cp /var/log/messages to /tmp. Using vi’s search and replace utility make each line begin with print “ and end with “;

Type “u” to undo all the changes

Copy /etc/lilo.conf to /tmp, edit this file and try to copy/paste yy/p and cut/paste with dd/p

Investigate the outcome of :x, ZZ, :quit, :wq, and :q! (which ones save and which one don't?)

Investigate the outcome for the various inserting modes: A, a, O, o, S and s

Optional: If you have time the vim-enhanced package installs a program called vimtutor which takes you through most common vi options.

The X Environment

Prerequisites	None

Goals

Understand the different components of the "Xwindows" environment

Recognise the function of each configuration file (no editing is expected)

Run applications on any display

Understand the function of a display manager including XDMCP

Contents

The X Environment	135

1. Introduction	136

2. Configuring X11R6	137

3. Controlling X clients	139

4. Starting X	140

5. The Display Manager	141

6. Troubleshooting X Clients	145

7. Choosing a Window Manager	145

9. Exercises and Summary	146

1. Introduction

The X Windows system was developed as the display component of Project Athena at the Massachusetts Institute of Technology. It is the graphical environment for UNIX. The X Window system for Linux is based on the freely distributable port of X Window version 11 release 6 (Commonly referred to as X11R6).

This freely distributable port is commonly known as xfree86 for the 80386/80486 and Pentium processor families. Since its initial port, Xfree86 has been ported to other computing platforms, including System V/386 and 386BSD.

X11R6 Components and Configuration Sections
client A client B wm X11R6 xfs monitor Section Files Section Monitor mouse keyboard video Section InputDevice Section InputDevice Section Device Section Pointer (old) Section "Keyboard" (old)

The above diagram shows the components of the X11R6 server. The “Section” names refer to configuration sections in the XF86Config configuration file (covered in the next section).

The two clients depicted on top of the server are so-called x-applications (e.g xclock or xterm). The window manager is also a client. Window managers add “windowing” facilities around the other x-application clients, allowing functionalities such as window dragging, focus, iconification, etc.

NOTICE:
The X11R6 server is independent from the clients that run on top. Clients are configured using specific configuration files or global files usually called Xdefaults or Xresources. The X server configuration file will only configure components such as the font server and font directories, mouse, keyboard, monitor resolution and color depth.

2. Configuring X11R6

Two of the configuration utilities provided with the Xfree86 software are the XF86Setup and xf86config scripts. Other vendors have specific utilities such as:

Xconfigurator, redhat-config-xfree86 (RedHat)

XFdrake (Mandrake)

sax (Suse)

Once the server has been configured one can change the horizontal and vertical settings for the monitor with xvidtune.

All the above mentioned configuration utilities will create and edit the XF86Config configuration file. This file is read at start up by the X Server and determines its behaviour. This file is typically found in the /etc/X11 directory, and this is its’ full path: /etc/X11/XF86Config.

There are 11 configuration sections in the config file, they are listed below:

ServerFlags

Module

InputDevice

Device

VideoAdapter

Monitor

Modes

Screen

ServerLayout

DRI

Vendor

NOTICE:
The obsolete section names Keyboard and Pointer are still recognised for compatability reasons, the new section name is now InputDevice

One of the first sections is the Section “Files”. The FontPath keyword tells whether to get fonts from a local directory or from a font server. The RgbPath keyword is used to indicate the full path to rgb text file used to map color names to RGB notation:

Section “Files”

FontPath “/path/to/fonts/dir/”

FontPath “trans/hostname:port”

RgbPath "/path/to/rgb"

EndSection

Where trans is the transport type unix, hostname is the fully qualified domain name of the font server, and port is the port to connect to, usually port 7100.

Example:

FontPath “unix/:7100”	# Local Font Server

FontPath “unix/myfontserver.mydomain.com:7100”

Below is a sample XF86Config file:

Section "Files"

RgbPath "/usr/X11R6/lib/X11/rgb"

FontPath "/usr/X11R6/lib/X11/fonts/misc:unscaled,/usr/X11R6/lib/X11/fonts/75dpi:unscaled,/usr/X11R6/lib/X11/fonts/100dpi:unscaled,/usr/X11R6/lib/X11/fonts/misc/"

EndSection

Section "InputDevice"

Identifier "Keyboard0"

Driver "keyboard"

EndSection

Section "InputDevice"

Identifier "Mouse0"

Driver "mouse"

Option "Protocol" "IMPS/2"

Option "Device" "/dev/psaux"

Option "ZAxisMapping" "4 5"

EndSection

Section "Monitor"

Identifier "Primary Monitor"

VendorName "Unknown"

ModelName "Unknown"

HorizSync 31.5-37.9

VertRefresh 55-90

Modeline "800x600" 40.00 800 840 968 1056 600 601 605 628 +hsync +vsync

EndSection

Section "Device"

Identifier "Primary Card"

VendorName "Unknown"

BoardName "None"

VideoRam 2048

EndSection

Section "Screen"

Driver "Accel"

Device "Primary Card"

Monitor "Primary Monitor"

DefaultColorDepth 24

BlankTime 0

SuspendTime 0

OffTime 0

SubSection "Display"

Depth 24

Modes "800x600"

EndSubSection

SubSection "Display"

Depth 32

Modes "800x600"

3. Controlling X clients

Setting Fonts and Colours

X clients are configured using the .Xresources or .Xdefaults file. These file are kept in the users home directory. It is not automatically created by default, as system-wide defaults are also available for each program.

Below is an extract from a .Xresources:

xterm_color*background: Black

xterm_color*foreground: Wheat

xterm_color*cursorColor: Orchid

xterm_color*reverseVideo: false

xterm_color*scrollBar: true

xterm_color*saveLines: 5000

xterm_color*reverseWrap: true

xterm_color*font: fixed

xterm_color.geometry: 80x25+20+20

xterm_color*fullCursor: true

xterm_color*scrollTtyOutput: off

xterm_color*scrollKey: on

term_color*VT100.Translations: #override\n\

<KeyPress>Prior : scroll-back(1,page)\n\

<KeyPress>Next : scroll-forw(1,page)

xterm_color*titleBar: false

Each of these directives is a system default directive that describes how a client will be displayed. Each line consists of the client name followed by an asterisk and the X Window parameter. Through a carefully configured .Xresources file the user can define the way a client will look each time it is started.

The DISPLAY Variable

When an x-application (or X client) is started it needs to know which X server to run on. An X server is referred to as a display. For example the first X server you start ( using startx for example) is called :0 the second would be called :1 and so on. The first X server (or display) running on the host 192.168.1.99 is called 192.168.1.99:0

Most native X clients such as xterm or xclock have a -display switch which can be used to set the display. But the easiest method is to set the environment variable called DISPLAY!

The next two commands are equivalent:

xclock -display 192.168.1.99:0

DISPLAY=192.168.1.99:0 xclock

However the X server on the host 192.168.1.99 will not allow this x-application to run. The user that started the X server on the remote host (192.168.1.99) needs to run the xhost command. This tool can selectively add or remove hosts to an access control list.

Example: Allow remote x-applications from host 192.168.1.7 to run on local server

xhost + 192.168.1.7 192.168.1.7 being added to access control list

NOTICE
The xhost mechanism must be used in conjunction with xauth (not part of the LPI objectives). For a remote x-client from 192.168.1.7 to run on our local server we still need to run the following on the local host: xauth extract - $DISPLAY | ssh 192.168.1.7 xauth merge - (Assuming that the user names are the same and that the hostname contained in $DISPLAY can be resolved)

4. Starting X

An X session can be started using 2 methods:

Method 1: From the command line, after logging in onto a virtual terminal the user launches the X Server

using a script called startx

Method 2: A Display Manager is running prompting the user with a graphical login, this is available for a specific runlevel (on RedHat type distributions this is runlevel 5).

1. From the Command Line

The startx script starts xinit. The xinit script has two main arguments (a) the X server and (b) the xinitrc script. The xinitrc script will source (read) the files Xresourses (controlling the x-applications) and the Xclients (choosing a window manager). So we can trace the startup sequence as follows:

startx --> xinit --> X -> xinitrc -> Xclients

2. Using a Display Manager

A display manager will automatically be started if the system is running in a given runlevel (e.g runlevel 5). We first describe the login process, the next section covers more advanced functionalities of a Display Manager. The login process follows the following steps:.

xdm --> xlogin --> Xsession --> (optionally) Xclients or ~/.Xclients

Different versions of display managers as well as different Linux distributions may use slightly different steps. In general however, note that startx uses xinit whereas xdm uses Xsession.

CUSTOMISING
Each user can further customise their environment by using a .xinitrc file. This file will be merged into the system xinitrc.
The switdesk tool allows users to define a custom .Xclients file

5. The Display Manager

There are three main display managers, xdm (generic), gdm (GNOME) and kdm (KDE). According to the LPI objectives the configuration files are in the following directories:

/etc/X11/xdm/

/etc/X11/gdm/

/etc/X11/kdm/ (see LPI objectives at the end of this manual p.162)

However, most often the configuration files for kdm are in /usr/share/config/kdm (also see below).

KDM

This display manager is installed with the KDE desktop environment. It is based on the generic xdm display manager and shares many common configuration files. These configuration files for are in /usr/share/config/kdm. The file that controls most functionalities is kdmrc.

The path to the kdm binary is /usr/bin/kdm

KDM Configuration files:

kdmrc Xaccess (same as xdm) Xservers (same as xdm) Xsession (same as xdm) Xsetup Xstartup

GDM

This display manager is distributed with the GNOME desktop environment. The main configuration file is gdm.conf

The path to the gdm binary is /usr/bin/gdm

GDM Configuration Files ( /etc/X11/gdm):

Sessions/ gdm.conf

XDM

The xdm display manager is part of the Xfree86 application. The main configuration file is xdm-config

The path to the xdm binary is /usr/bin/xdm

XDM Configuration Files:

Xaccess Xresources Xsession xdm-config Xservers _

We will look at the xdm configuration files in more detail later in this section.

Display Managers are used mainly in run level 5:

Set default runlevel in /etc/inittab
id:5:initdefault:

Display managers allow local users to log onto the system using the graphical interface. They can also be used to provide a graphical login interface over the network. For this they use a protocol called XDMCP or X Display Manager Control Protocol. By default XDMCP is disabled (we will enable XDMCP as an exercise).

X server and Display Manager
Welcome !! Display Manager (x-application) xlogin login password X11R6

Configuration Files

/etc/X11/xdm/Xrescources

Since the Display Manager is also an x-application, the fonts, the background colors and xlogin

can be configured with the Xresourses file in /etc/X11/xdm/. When using gdm, the

/etc/X11/gdm/Init/Default script will source Xresources.

/etc/X11/xdm/Xservers

This file simply maps the name of a display with an X server. For example display :0 is understood

to be the local X server. Remember that X always runs on the first free /dev/tty.

/etc/X11/xdm/xdm-config

This is the main configuration file for xdm. It is also used to enable XDMCP (see exercises)

/etc/X11/xdm/Xaccess

This file is used to enable XDMCP, allowing remote hosts to directly connect to the local server

( using -query) or query about other display

The Xaccess file
# $XConsortium: Xaccess,v 1.5 91/08/26 11:52:51 rws Exp $
#
# Access control file for XDMCP connections
# To control Direct and Broadcast access:
#
# pattern
#
# To control Indirect queries:
#
# pattern list of hostnames and/or macros ...
#
# To use the chooser:
#
# pattern CHOOSER BROADCAST
#
# or
#
# pattern CHOOSER list of hostnames and/or macros ...
#
# To define macros:
#
# %name list of hosts ...
#
# The first form tells xdm which displays to respond to itself.
# The second form tells xdm to forward indirect queries from hosts matching
# the specified pattern to the indicated list of hosts.
# The third form tells xdm to handle indirect queries using the chooser;
# the chooser is directed to send its own queries out via the broadcast
# address and display the results on the terminal.
# The fourth form is similar to the third, except instead of using the
# broadcast address, it sends DirectQuerys to each of the hosts in the list
#
# In all cases, xdm uses the first entry which matches the terminal;
# for IndirectQuery messages only entries with right hand sides can
# match, for Direct and Broadcast Query messages, only entries without
# right hand sides can match.
#
* #any host can get a login window
#
# To hardwire a specific terminal to a specific host, you can
# leave the terminal sending indirect queries to this host, and
# use an entry of the form:
#
#terminal-a host-a
# The nicest way to run the chooser is to just ask it to broadcast
# requests to the network - that way new hosts show up automatically.
# Sometimes, however, the chooser can't figure out how to broadcast,
# so this may not work in all environments.
#
* CHOOSER BROADCAST #any indirect host can get a chooser
# If you'd prefer to configure the set of hosts each terminal sees,
# then just uncomment these lines (and comment the CHOOSER line above)
# and edit the %hostlist line as appropriate
#
#%hostlist host-a host-b
#* CHOOSER %hostlist #

The Xservers file
# $XConsortium: Xserv.ws.cpp,v 1.3 93/09/28 14:30:30 gildea Exp $
#
#
# $XFree86: xc/programs/xdm/config/Xserv.ws.cpp,v 1.1.1.1.12.2 1998/10/04 15:23:14 hohndel Exp $
#
# Xservers file, workstation prototype
#
# This file should contain an entry to start the server on the
# local display; if you have more than one display (not screen),
# you can add entries to the list (one per line). If you also
# have some X terminals connected which do not support XDMCP,
# you can add them here as well. Each X terminal line should
# look like:
# XTerminalName:0 foreign
#
:0 local /usr/X11R6/bin/X

Since the Display Manager is also an x-application the Xrescources file is similar to the .Xrescources file except that it controls how the login screen is displayed .

Sample Xrescources file
! $XConsortium: Xresources /main/8 1996/11/11 09:24:46 swick $
xlogin*borderWidth: 3
xlogin*greeting: CLIENTHOST
xlogin*namePrompt: login:\040
xlogin*fail: Login incorrect
#ifdef COLOR
xlogin*greetColor: CadetBlue
xlogin*failColor: red
*Foreground: black
*Background: #fffff0
#else
xlogin*Foreground: black
xlogin*Background: white
#endif
XConsole.text.geometry: 480x130
XConsole.verbose: true
XConsole*iconic: true
XConsole*font: fixed

Sample xdm-config file
! $XFree86: xc/programs/xdm/config/xdm-conf.cpp,v 1.1.1.2.4.2 1999/10/12 18:33:29 hohndel Exp $
!
DisplayManager.servers: /etc/X11/xdm/Xservers
DisplayManager.accessFile: /etc/X11/xdm/Xaccess
! All displays should use authorization, but we cannot be sure
! X terminals will be configured that way, so by default
! use authorization only for local displays :0, :1, etc.
DisplayManager._0.authorize: true
DisplayManager._1.authorize: true
!
DisplayManager*resources: /etc/X11/xdm/Xresources
DisplayManager*session: /etc/X11/xdm/Xsession
DisplayManager*authComplain: false
! SECURITY: do not listen for XDMCP or Chooser requests
! Comment out this line if you want to manage X terminals with xdm
DisplayManager.requestPort: 0

6. Troubleshooting X Clients

Occasionally X Clients wont terminate properly leaving zombie processes. A zombie process in one whose parent processes has terminated, and cannot clear references to the child process. When a child process’ parent exits leaving the child process still running, this is usually visible by running ps which will reveal the child process being owned by PID 1 (init). These processes should be killed because they may be using CPU resources. Killing such a process requires the user to be the user who owns the process, or root. It might be necessary to use the –9 option to actually kill these processes.

7. Choosing a Window Manager

The area that is commonly referred to as the desktop is also known in the X Window world as the screen. It covers the entire area of your monitor display. The root window is the background of your screen, typically used to display a colour or picture. The window manager provides an interface between the user and the X server. It is virtually impossible to use X without a window manager, because it provides the title bar and the familiar buttons with which you manipulate the display.

Information on available window managers is available from the Window Managers website at http://www.PliG.org/xwinman. Many of the Linux versions of these window managers are available at ftp://metalab.unc.edu/pub/Linux/X11/window-managers.

In addition to the different window managers there are also various desktop environments, among which the most common are KDE, GNOME and XFCE.

Below is a brief list of integrated window managers:

Enlightenment

fvwm

icewm

amiWM

mlvwm

dfm

olwm

olvwm

mwm

Window Maker

9. Exercises and Summary

Review Questions (answers p.151)

Yes or No

1. The configuration file for a window manager is XF86Config	____

2. An x-client can be configured to run on any X server accessible on a network	____

3. A display manager is a program that manages pixels when using a

windowing environment	____

4. A user running an X server can disable access control using xhost	____

5. The XDMCP protocol is used by display managers to display a graphical login

on remote computers	____

6. If a system is not running a display manager one usually starts a windowing

environment with the xinit tool	____

Glossary

Term	Definition
DISPLAY	Shell environmental variable used to notify x-applications which display (in this case, which X server) to run on
XDMCP	a protocol that provides a uniform mechanism for an autonomous display to request login service from a remote host
run level	a software configuration of the system which allows only a selected group of processes to exist – see init(8)
x-client or x-application	In this manual the terms are used to describe applications such as xterm or xclock that run on an X server
desktop environment	a suite of applications (including a window manager) originally designed to use the entire surface of the screen as a 'desktop'. Integrated applications often include features such as short cuts for copy pasting, drag and drop, etc. Example desktops are XFCE, GNOME and KDE
display manager	an x-application which runs at a specific run level (often run level 5) displaying a graphical login interface. Display managers also handle the XDMCP protocol. Most common display managers are xdm (generic X11R6), gdm (part of the GNOME desktop suite) and kdm (part of the KDE desktop suite)
window manager	a special x-application which can move, resize or iconify windows. In some cases window managers also provide a task bar as well as drop down menus for quick launch. Examples are twm, fluxbox, icewm etc ...
session manager	provides a way to save a window session once the user logs out

X11 Configuration File

File	Description
XF86Config	main configuration file for the X11R6 server

Display Manager Configuration Files

System File	Description
gdm.conf	main configuration file for gdm
kdmrc	main configuration file for kdm
Xaccess	one of the files used to allow/disallow XDMCP access
xdm-config	main configuration file for xdm
Xrescources	customisation file used by display managers
Xservers	configures how many display managers to start on a system. The file associates a display (default :0) to a server (usually X11R6)
Xsession	script used by display managers to start a specific windowing environment
Xclients	script used by Xsession as well as xdm to start a system wide windowing environment

User Customisations

File	Description
~/.Xresources ~/.Xdefaults	files used to control the way x-applications start (e.g position, font size, colours, etc)
~/.xinitrc	when using startx users can specify which window manager or desktop environment to start
~/.Xclients	when using a display manager users can specify which window manager or desktop environment to start

Commands

Command	Description
gdm p.141	gdm(1) - GDM is a replacement for XDM, the X Display Manager. Unlike its competitors (X3DM, KDM, WDM) GDM was written from scratch and does not contain any original XDM / X Consortium code. GDM runs and manages the X servers for both local and remote logins (using XDMCP)
kdm p.141	a display manager provided by the KDE desktop, it has many configuration files in common with xdm
startx p.140	a script that calls xinit and starts the X Window System, that is an X server together with a window manager or a desktop
xauth p.140	(not an LPI objective) xauth(1) - The xauth program is used to edit and display the authorization information used in connecting to the X server. Normally xauth is not used to create the authority file entry in the first place; xdm does that – see also pam_xauth(8) for further reading
xdm p.141	the X Display Manager made available as part of the X server
xf86config p.137	program that interactively creates a XF86Config file
XF86Setup p.137	graphical program that interactively creates or modifies an XF86Config file
xhost p.139	xhost(1) - The xhost program is used to add and delete host names or user names to the list allowed to make connections to the X server. In the case of hosts, this provides a rudimentary form of privacy control and security. It is only sufficient for a workstation (single user) environment,
xinit p.140	xinit(1) - The xinit program is used to start the X Window System server and a first client program (usually a window manager) on systems that cannot start X directly from /etc/init or in environments that use multiple window systems. When this first client exits, xinit will kill the X server and then terminate
xinitrc p.140	script launched by xinit containing a list of clients to be started. Additional clients (such as terminals, clocks, etc) should be started in the background. The first client however (usually the window manager) should be started in the forground in order to prevent xinitrc from exiting – see xinit(1)
xvidtune p.137	xvidtune(1) - Without any options it presents the user with various buttons and sliders that can be used to interactively adjust existing video modes. It will also print the settings in a format suitable for inclusion in an XF86Config file

Exercises

Before starting make sure you are running in runlevel 3.

init 3

1. Log into a virtual terminal (e.g Alt+F1)

2. As root save the existing configuration file /etc/X11/XF86Config and try out the various configuration tools:

Redhat: Xconfigurator, redhat-config-xfree86 (8.0)

Mandrake : XFdrake

Suse: sax

XF86Setup

xf86config

X (this is the X11 server itself, use the -configure flag)

3. Start the X server by typing X. This will start X11R6 alone with no window managers. Return to a virtual terminal (e.g Ctrl+Alt+F2) and get the command line back. Then do the following:

export DISPLAY=localhost:0

xterm&

Go back into X by typing Ctrl+Alt+F7 (if you haven’t changed the defaults in /etc/inittab...). You should have an xterminal running. Next type in this terminal:

twm&

What has happened? Can you kill twm without killing X? Go back to a

virtual terminal (e.g Ctrl+Alt+F2) and type:

X :1

Log into another virtual terminal (e.g tty3) and type:

export DISPLAY=:1; xterm&

You now have two X servers running on screen 0 and 1. How do you switch from one to another?

4. Setting up XDMCP

For this to work make sure the line containing an ‘*’ is uncommented in /etc/X11/xdm/Xaccess.

If you are using xdm or kdm comment out the line in xdm-config as follows

!DisplayManager.requestPort: 0

This line is originally uncommented and allows only local login requests on screen 0 (more secure).

If you are using gdm then you will also need to edit gdm.conf and put

enable=true

This will turn off the default security settings for gdm.

If your IP is 1.2.3.4 then users on your network can start an X session with:

X –query 1.2.3.4 :1

or

X -indirect 1.2.3.4 :1

Answers to Revision Questions

Installation (p.8)

1.No – the rawrite tool runs under DOS. The tool used to copy image files onto a block device is dd

2.Yes – any device that can hold data (i.e not an extended partition) can be used as the root device

Hardware Suppport (p.24)

1. No – the root filesystem can be on any disk type

2. No – the kernel module only handles the USB controller. The kernel will notify events to a USB user agent which then uses user-maps to configure the particular device

Managing Devices (p.36)

1. No – you need to re-run /sbin/lilo every time you change something in /etc/lilo.conf

2. Yes – GRUB only need to be installed once

3. No – the 1024 cylinder limit affects the second stage bootloader

4. Yes – one cannot set quotas on a directory

The Linux Filesystem (p.52)

1. No – programs stored in /usr/ are not essential for booting up the system

2. No – a user's home directory can be anywhere on the system

3. Yes

The Command Line (p.67)

1. Yes

2. No – STDOUT can be redirected to a file

3. Yes

4. No – commands are generally stored in a file called .bash_history in the user's home directory

File Management (p.78)

1. Yes

2. No – cd with no argument will also go to the user's home directory

3. No – you must use 'mkdir -p' to make directories which contain subdirectories

4. Yes

5. No – the correct command is 'ln -s FILE FILE-LINK '

6. No – paths beginning with a forward slash are absolute paths

Process Management (p.87)

1. No – kill will send a signal, some signals may simply pause a process, others force daemons to re-read their configuration file. However the default signal (15 or SIGTERM) will attempt to terminate a process.

2. Yes

3. Yes

4. No

Text Processing (p.97)

1. Yes

2. No – use tail

3. Yes – this is the case with all the text tools

4. No – all the text tools print the altered data to STDOUT and don't alter the original file

Software Installation (p.118)

1. No – one uses make

2. Yes – a makefile is unique for each project. The make tool will only read a makefile in the current directory (i.e the directory the make command is started from)

3. Yes

4. Yes

5. Yes

6. No

7. Yes

Advanced Text Manipulation (p.126)

1. Yes – the "e?" expression reads 'match 0 or 1 e'

2. Yes – the "a*" expression reads ' match 0 or any a'

3. Yes – the "e+" expressiom reads 'match at least 1 or any e'

4. Yes – notice that the "a*" is at the end of the expression. This means that 'baz' followed by anything will also be matched

Using vi (p.133)

1. No – look at the position of hjkl on the keyboard. The l key is on the right and will cause the cursor to move to the right

2. Yes

3. No – 3w will move the cursor three words forward, then d is an incomplete command. Deleting three words can be done with d3w

4. No – the commands :qw will be read from left to right. So quit (q) must always be last

The X Environment (p.146)

1. No – the XF86Config file only configures the X server. Window managers often use directories stored in user's home directories

2. Yes – this is true although firewalls can prevent x-applications to connect to remote X servers

3. No – a display manager handles login access on a display (local X server or remote X server using XDMCP)

4.Yes – note that on most of the recent Linux distributions xhost must be used in conjunction with xauth

5. Yes

6. No – one usually uses startx

LPI 101 Objectives

http://www.lpi.org/en/obj_101.html

Thu Nov 4 04:45:58 2004

Exam 101: Detailed Objectives

This is a required exam for LPI certification Level 1. It covers basic system administration skills that are common across all distributions of Linux.

Each objective is assigned a weighting value. The weights range roughly from 1 to 10, and indicate the relative importance of each objective. Objectives with higher weights will be covered in the exam with more questions.

Topic 101: Hardware & Architecture

* 1.101.1 Configure Fundamental BIOS Settings

Modified: 2003-March-17

Maintainer: Kara Pritchard

Weight: 1

Description: Candidates should be able to configure fundamental system hardware by making the correct settings in the system BIOS. This objective includes a proper understanding of BIOS configuration issues such as the use of LBA on IDE hard disks larger than 1024 cylinders, enabling or disabling integrated peripherals, as well as configuring systems with (or without) external peripherals such as keyboards. It also includes the correct setting for IRQ, DMA and I/O addresses for all BIOS administrated ports and settings for error handling (p. 11).

Key files, terms, and utilities include:

/proc/ioports (p. 11)

/proc/interrupts (p. 11)

/proc/dma (p. 11)

/proc/pci (p. 11)

* 1.101.3 Configure Modem and Sound cards

Modified: 2003-March-17

Maintainer: Kara Pritchard

Weight: 1

Description: Ensure devices meet compatibility requirements (particularly that the modem is NOT a win-modem), verify that both the modem and sound card are using unique and correct IRQ's, I/O, and DMA addresses, if the sound card is PnP install and run sndconfig (p.22)and isapnp (p.12), configure modem for outbound dial-up, configure modem for outbound PPP | SLIP | CSLIP connection, set serial port for 115.2 Kbps (p.18)

* 1.101.4 Setup SCSI Devices

Modified: 2003-March-17

Maintainer: Kara Pritchard

Weight: 1

Description: Candidates should be able to configure SCSI devices using the SCSI BIOS as well as the necessary Linux tools. They also should be able to differentiate between the various types of SCSI. This objective includes manipulating the SCSI BIOS to detect used and available SCSI IDs and setting the correct ID number for different devices especially the boot device. It also includes managing the settings in the computer's BIOS to determine the desired boot sequence if both SCSI and IDE drives are used.

Key files, terms, and utilities include:

SCSI ID(p.14)

/proc/scsi/(p.15)

scsi_info(p.15)

* 1.101.5 Setup different PC expansion cards

Modified: 2003-March-17

Maintainer: Kara Pritchard

Weight: 3

Description: Candidates should be able to configure various cards for the various expansion slots. They should know the differences between ISA and PCI cards with respect to configuration issues. This objective includes the correct settings of IRQs, DMAs and I/O Ports of the cards, especially to avoid conflicts between devices. It also includes using isapnp if the card is an ISA PnP device.

Key files, terms, and utilities include:

/proc/dma

/proc/interrupts

/proc/ioports

/proc/pci

pnpdump(8) (p.12)

isapnp(8) (p.12)

lspci(8) (p.11)

* 1.101.6 Configure Communication Devices

Modified: 2003-March-17

Maintainer: Kara Pritchard

Weight: 1

Description: Candidates should be able to install and configure different internal and external communication devices like modems, ISDN adapters (p.20), and DSL switches (p.20). This objective includes verification of compatibility requirements (especially important if that modem is a winmodem [p.19]), necessary hardware settings for internal devices (IRQs, DMAs, I/O ports), and loading and configuring suitable device drivers. It also includes communication device and interface configuration requirements, such as the right serial port for 115.2 Kbps (p.18), and the correct modem settings for outbound PPP connection(s) (p.18).

Key files, terms, and utilities include:

/proc/dma

/proc/interrupts

/proc/ioports

setserial(8)

* 1.101.7 Configure USB devices

Modified: 2003-March-17

Maintainer: Kara Pritchard

Weight: 1

Description: Candidates should be able to activate USB support, use and configure different USB devices. This objective includes the correct selection of the USB chipset and the corresponding module. It also includes the knowledge of the basic architecture of the layer model of USB as well as the different modules used in the different layers.

Key files, terms, and utilities include:

lspci(8)

usb-uhci.o(p.13)

usb-ohci.o(p.13)

/etc/usbmgr/(p.14

usbmodules

/etc/hotplug(p.13)

Topic 102: Linux Installation & Package Management

* 1.102.1 Design hard disk layout

Modified: 2003-March-17

Maintainer: Kara Pritchard

Weight: 5

Description: Candidates should be able to design a disk partitioning scheme for a Linux system. This objective includes allocating filesystems or swap space to separate partitions or disks, and tailoring the design to the intended use of the system. It also includes placing /boot on a partition that conforms with the BIOS' requirements for booting.

Key files, terms, and utilities include:

/ (root) filesystem (p.5 and p.40)

/var filesystem (p.41)

/home filesystem (p.41)

swap space (p.6)

mount points (p.5)

partitions (p.5, p.28)

cylinder 1024 (p.32 and p.36)

* 1.102.2 Install a boot manager

Modified: 2003-March-17

Maintainer: Kara Pritchard

Weight: 1

Description: Candidate should be able to select, install, and configure a boot manager. This objective includes providing alternative boot locations and backup boot options (for example, using a boot floppy).

Key files, terms, and utilities include:

/etc/lilo.conf (p.32)

/boot/grub/grub.conf (p.32)

lilo (p.32)

grub-install (p.32)

MBR (p.31)

superblock (p.42)

first stage boot loader (p.31)

* 1.102.3 Make and install programs from source

Modified: 2003-March-17

Maintainer: Kara Pritchard

Weight: 5

Description: Candidates should be able to build and install an executable program from source. This objective includes being able to unpack a file of sources. Candidates should be able to make simple customizations to the Makefile, for example changing paths or adding extra include directories.

Key files, terms, and utilities include:

gunzip

gzip (p.105)

bzip2 (p.105)

tar (p.106)

configure (p.107)

make (p.107)

* 1.102.4 Manage shared libraries

Modified: 2003-March-17

Maintainer: Kara Pritchard

Weight: 3

Description: Candidates should be able to determine the shared libraries that executable programs depend on and install them when necessary. Candidates should be able to state where system libraries are kept.

Key files, terms, and utilities include:

ldd (p.103)

ldconfig (p.104)

/etc/ld.so.conf (p.104)

LD_LIBRARY_PATH (p.104)

* 1.102.5 Use Debian package management

Modified: 2003-March-17

Maintainer: Kara Pritchard

Weight: 8

Description: Candidates should be able to perform package management skills using the Debian package manager. This objective includes being able to use command-line and interactive tools to install, upgrade, or uninstall packages, as well as find packages containing specific files or software (such packages might or might not be installed). This objective also includes being able to obtain package information like version, content, dependencies, package integrity and installation status (whether or not the package is installed).

Key files, terms, and utilities include:

unpack (p.114, p.114, p.115)

configure (p.114, p.115)

/etc/dpkg/dpkg.cfg (p.114)

/var/lib/dpkg/* (p.115)

/etc/apt/apt.conf (p.116)

/etc/apt/sources.list (p.116)

dpkg (p.113, .115)

dselect (p.113)

dpkg-reconfigure

apt-get (p.116)

alien (p.117, p.119)

* 1.102.6 Use Red Hat Package Manager (RPM)

Modified: 2003-March-17

Maintainer: Kara Pritchard

Weight: 8

Description: Candidates should be able to perform package management under Linux distributions that use RPMs for package distribution. This objective includes being able to install, re-install, upgrade, and remove packages, as well as obtain status and version information on packages. This objective also includes obtaining package information such as version, status, dependencies, integrity, and signatures. Candidates should be able to determine what files a package provides, as well as find which package a specific file comes from.

Key files, terms, and utilities include:

/etc/rpmrc (p.119)

/usr/lib/rpm/* (p.119)

rpm (p.108, p.119)

grep

Topic 103: GNU & Unix Commands

* 1.103.1 Work on the command line

Modified: 2003-March-17

Maintainer: Kara Pritchard

Weight: 5

Description: Candidates should be able to Interact with shells and commands using the command line. This includes typing valid commands and command sequences, defining, referencing and exporting environment variables, using command history and editing facilities, invoking commands in the path and outside the path, using command substitution, applying commands recursively through a directory tree and using man to find out about commands.

Key files, terms, and utilities include:

.

bash

echo (p.57)

env (p.58)

exec (p.64)

export (p.58)

man (p.66, p.65)

pwd (p.72)

set (p.58)

unset (p.58)

~/.bash_history (p.63)

~/.profile

* 1.103.2 Process text streams using filters

Modified: 2003-March-17

Maintainer: Kara Pritchard

Weight: 6

Description: Candidates should should be able to apply filters to text streams. Tasks include sending text files and output streams through text utility filters to modify the output, and using standard UNIX commands found in the GNU textutils package.

Key files, terms, and utilities include:

cat (p.91)

cut (p.94)

expand (p.93)

fmt (p.95)

head (p.92)

join (p.95)

nl (p.93)

od (p.93)

paste (p.95)

pr (p.96)

sed (p.124)

sort (p.95)

split (p.93)

tac (p.91)

tail (p.92)

tr (p.96)

unexpand (p.93)

uniq (p.94)

wc (p.92)

* 1.103.3 Perform basic file management

Modified: 2003-March-17

Maintainer: Kara Pritchard

Weight: 3

Description: Candidates should be able to use the basic UNIX commands to copy, move, and remove files and directories. Tasks include advanced file management operations such as copying multiple files recursively, removing directories recursively, and moving files that meet a wildcard pattern. This includes using simple and advanced wildcard specifications to refer to files, as well as using find to locate and act on files based on type, size, or time.

Key files, terms, and utilities include:

cp (p.74)

find (p.72)

mkdir (p.74)

mv (p.75)

ls (p.73)

rm (p.74)

rmdir(p.74)

touch (p.76)

file globbing (p.67)

* 1.103.4 Use streams, pipes, and redirects

Modified: 2003-March-17

Maintainer: Kara Pritchard

Weight: 5

Description: Candidates should be able to redirect streams and connect them in order to efficiently process textual data. Tasks include redirecting standard input, standard output, and standard error, piping the output of one command to the input of another command, using the output of one command as arguments to another command and sending output to both stdout and a file.

Key files, terms, and utilities include:

tee (p.62)

xargs (p.72)

< (p.60)

<< (p.64)

>(p.60)

>>(p.60)

| (p.61)

` ` (p.63)

* 1.103.5 Create, monitor, and kill processes

Modified: 2003-March-17

Maintainer: Kara Pritchard

Weight: 5

Description: Candidates should be able to manage processes. This includes knowing how to run jobs in the foreground and background, bring a job from the background to the foreground and vice versa, start a process that will run without being connected to a terminal and signal a program to continue running after logout. Tasks also include monitoring active processes, selecting and sorting processes for display, sending signals to processes, killing processes and identifying and killing X applications that did not terminate after the X session closed.

Key files, terms, and utilities include:

& (p.86)

bg (p.85)

fg (p.85)

jobs (p.86)

kill (p.83)

nohup (p.86)

ps (p.82)

top (p.83)

* 1.103.6 Modify process execution priorities

Modified: 2003-March-17

Maintainer: Kara Pritchard

Weight: 3

Description: Candidates should should be able to manage process execution priorities. Tasks include running a program with higher or lower priority, determining the priority of a process and changing the priority of a running process.

Key files, terms, and utilities include:

nice (p.84)

ps (p.82)

renice (p.85)

top (p.83)

* 1.103.7 Search text files using regular expressions

Modified: 2003-March-17

Maintainer: Kara Pritchard

Weight: 3

Description: Candidates should be able to manipulate files and text data using regular expressions. This objective includes creating simple regular expressions containing several notational elements. It also includes using regular expression tools to perform searches through a filesystem or file content.

Key files, terms, and utilities include:

grep (p.122)

regexp ()

sed (p.124)

* 1.103.8 Perform basic file editing operations using vi

Modified: 2003-March-17

Maintainer: Kara Pritchard

Weight: 1

Description: Candidates should be able to edit text files using vi. This objective includes vi navigation, basic vi nodes, inserting, editing, deleting, copying, and finding text.

Key files, terms, and utilities include:

vi (p.129)

/ (p.131), ? (p.131)

h,j,k,l (p.129)

G, H, L

i (p.130), c (p130), d, dd (p.130), p (p.130), o (p.130), a (p.130)

ZZ (p.132), :w! (p.132), :q! (p.132), :e! (p.132)

:! (p.132)

Topic 104: Devices, Linux Filesystems, Filesystem Hierarchy Standard

* 1.104.1 Create partitions and filesystems

Modified: 2003-March-17

Maintainer: Kara Pritchard

Weight: 3

Description: Candidates should be able to configure disk partitions and then create filesystems on media such as hard disks. This objective includes using various mkfs commands to set up partitions to various filesystems, including ext2, ext3, reiserfs, vfat, and xfs.

Key files, terms, and utilities include:

fdisk (p.29)

mkfs (p.42)

* 1.104.2 Maintain the integrity of filesystems

Modified: 2003-March-17

Maintainer: Kara Pritchard

Weight: 3

Description: Candidates should be able to verify the integrity of filesystems, monitor free space and inodes, and repair simple filesystem problems. This objective includes the commands required to maintain a standard filesystem, as well as the extra data associated with a journaling filesystem.

Key files, terms, and utilities include:

du (p.45)

df (p.45)

fsck (p.43)

e2fsck (p.43)

mke2fs (p.42)

debugfs (p.43)

dumpe2fs (p.43)

tune2fs (p.34)

* 1.104.3 Control mounting and unmounting filesystems

Modified: 2003-March-17

Maintainer: Kara Pritchard

Weight: 3

Description: Candidates should be able to configure the mounting of a filesystem. This objective includes the ability to manually mount and unmount filesystems, configure filesystem mounting on bootup, and configure user mountable removeable filesystems such as tape drives, floppies, and CDs.

Key files, terms, and utilities include:

/etc/fstab (p.33)

mount (p.33)

umount (p.34)

* 1.104.4 Managing disk quota

Modified: 2003-March-17

Maintainer: Kara Pritchard

Weight: 3

Description: Candidates should be able to manage disk quotas for users. This objective includes setting up a disk quota for a filesystem, editing, checking, and generating user quota reports.

Key files, terms, and utilities include:

quota (p.35)

edquota (p.35)

repquota (p.35)

quotaon (p.35)

* 1.104.5 Use file permissions to control access to files

Modified: 2003-March-17

Maintainer: Kara Pritchard

Weight: 5

Description: Candidates should be able to control file access through permissions. This objective includes access permissions on regular and special files as well as directories. Also included are access modes such as suid, sgid, and the sticky bit, the use of the group field to grant file access to workgroups, the immutable flag, and the default file creation mode.

Key files, terms, and utilities include:

chmod (p.46)

umask (p.47)

chattr (p.49)

* 1.104.6 Manage file ownership

Modified: 2003-March-17

Maintainer: Kara Pritchard

Weight: 1

Description: Candidates should be able to control user and group ownership of files. This objective includes the ability to change the user and group owner of a file as well as the default group owner for new files.

Key files, terms, and utilities include:

chmod (p. 46)

chown (p.46)

chgrp (p.46)

* 1.104.7 Create and change hard and symbolic links

Modified: 2003-March-17

Maintainer: Kara Pritchard

Weight: 1

Description: Candidates should be able to create and manage hard and symbolic links to a file. This objective includes the ability to create and identify links, copy files through links, and use linked files to support system administration tasks.

Key files, terms, and utilities include:

ln (p.75)

* 1.104.8 Find system files and place files in the correct location

Modified: 2003-March-17

Maintainer: Kara Pritchard

Weight: 5

Description: Candidates should be thouroughly familiar with the Filesystem Hierarchy Standard, including typical file locations and directory classifications. This objective includes the ability to find files and commands on a Linux system.

Key files, terms, and utilities include:

find (p.72)

locate (p.73)

slocate (p.73)

updatedb (p.73)

whereis (p.73)

which (p.73)

/etc/updatedb.conf (p.73)

Topic 110: The X Window System

* 1.110.1 Install & Configure XFree86

Modified: 2003-March-17

Maintainer: Kara Pritchard

Weight: 5

Description: Candidate should be able to configure and install X and an X font server. This objective includes verifying that the video card and monitor are supported by an X server, as well as customizing and tuning X for the videocard and monitor. It also includes installing an X font server, installing fonts, and configuring X to use the font server (may require a manual edit of /etc/X11/XF86Config in the "Files" section).

Key files, terms, and utilities include:

XF86Setup (p.137)

xf86config (p.137)

xvidtune (p.137)

/etc/X11/XF86Config (p.)

.Xresources (p.139)

* 1.110.2 Setup a display manager

Modified: 2003-March-17

Maintainer: Kara Pritchard

Weight: 3

Description: Candidate should be able setup and customize a Display manager. This objective includes turning the display manager on or off and changing the display manager greeting. This objective includes changing default bitplanes for the display manager. It also includes configuring display managers for use by X-stations. This objective covers the display managers XDM (X Display Manger), GDM (Gnome Display Manager) and KDM (KDE Display Manager).

Key files, terms, and utilities include:

/etc/inittab

/etc/X11/xdm/* (p.141)

/etc/X11/kdm/* (p.141)

/etc/X11/gdm/* (p.141)

* 1.110.4 Install & Customize a Window Manager Environment

Modified: 2003-March-17

Maintainer: Kara Pritchard

Weight: 5

Description: Candidate should be able to customize a system-wide desktop environment and/or window manager, to demonstrate an understanding of customization procedures for window manager menus and/or desktop panel menus. This objective includes selecting and configuring the desired x-terminal (xterm, rxvt, aterm etc.), verifying and resolving library dependency issues for X applications, exporting X-display to a client workstation.

Key files, terms, and utilities include:

.xinitrc (p.140)

.Xdefaults (p.139)

xhost (p.139)

DISPLAY environment variable (p.139)

http://www.lpi.org/en/obj_101.html

Copyright © 1999, 2000, 2001, 2002, 2003 Linux Professional Institute. All rights reserved.

Copyright (c) 2004 LinuxIT.

Permission is granted to copy, distribute and/or modify this document

under the terms of the GNU Free Documentation License, Version 1.2

or any later version published by the Free Software Foundation;

with the Invariant Sections being History, Acknowledgements, with the	Front-Cover Texts being “released under the GFDL by LinuxIT”.

GNU Free Documentation License

Version 1.2, November 2002

Copyright (C) 2000,2001,2002 Free Software Foundation, Inc.

51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA

Everyone is permitted to copy and distribute verbatim copies

of this license document, but changing it is not allowed

0. PREAMBLE

The purpose of this License is to make a manual, textbook, or other functional and useful document "free" in the sense of freedom: to assure everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or noncommercially. Secondarily, this License preserves for the author and publisher a way to get credit for their work, while not being considered responsible for modifications made by others.

This License is a kind of "copyleft", which means that derivative works of the document must themselves be free in the same sense. It complements the GNU General Public License, which is a copyleft license designed for free software.

We have designed this License in order to use it for manuals for free software, because free software needs free documentation: a free program should come with manuals providing the same freedoms that the software does. But this License is not limited to software manuals; it can be used for any textual work, regardless of subject matter or whether it is published as a printed book. We recommend this License principally for works whose purpose is instruction or reference.

1. APPLICABILITY AND DEFINITIONS

This License applies to any manual or other work, in any medium, that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License. Such a notice grants a world-wide, royalty-free license, unlimited in duration, to use that work under the conditions stated herein. The "Document", below, refers to any such manual or work. Any member of the public is a licensee, and is addressed as "you". You accept the license if you copy, modify or distribute the work in a way requiring permission under copyright law.

A "Modified Version" of the Document means any work containing the Document or a portion of it, either copied verbatim, or with modifications and/or translated into another language.

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The "Invariant Sections" are certain Secondary Sections whose titles are designated, as being those of Invariant Sections, in the notice that says that the Document is released under this License. If a section does not fit the above definition of Secondary then it is not allowed to be designated as Invariant. The Document may contain zero Invariant Sections. If the Document does not identify any Invariant Sections then there are none.

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The "Title Page" means, for a printed book, the title page itself, plus such following pages as are needed to hold, legibly, the material this License requires to appear in the title page. For works in formats which do not have any title page as such, "Title Page" means the text near the most prominent appearance of the work's title, preceding the beginning of the body of the text.

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2. VERBATIM COPYING

You may copy and distribute the Document in any medium, either commercially or noncommercially, provided that this License, the copyright notices, and the license notice saying this License applies to the Document are reproduced in all copies, and that you add no other conditions whatsoever to those of this License. You may not use technical measures to obstruct or control the reading or further copying of the copies you make or distribute. However, you may accept compensation in exchange for copies. If you distribute a large enough number of copies you must also follow the conditions in section 3.

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3. COPYING IN QUANTITY

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4. MODIFICATIONS

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E. Add an appropriate copyright notice for your modifications adjacent to the other copyright notices.

F. Include, immediately after the copyright notices, a license notice giving the public permission to use the Modified Version under the terms of this License, in the form shown in the Addendum below.

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H. Include an unaltered copy of this License.

I. Preserve the section Entitled "History", Preserve its Title, and add to it an item stating at least the title, year, new authors, and publisher of the Modified Version as given on the Title Page. If there is no section Entitled "History" in the Document, create one stating the title, year, authors, and publisher of the Document as given on its Title Page, then add an item describing the Modified Version as stated in the previous sentence.

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K. For any section Entitled "Acknowledgements" or "Dedications", Preserve the Title of the section, and preserve in the section all the substance and tone of each of the contributor acknowledgements and/or dedications given therein.

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5. COMBINING DOCUMENTS

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In the combination, you must combine any sections Entitled "History" in the various original documents, forming one section Entitled "History"; likewise combine any sections Entitled "Acknowledgements", and any sections Entitled "Dedications". You must delete all sections Entitled "Endorsements."

6. COLLECTIONS OF DOCUMENTS

You may make a collection consisting of the Document and other documents released under this License, and replace the individual copies of this License in the various documents with a single copy that is included in the collection, provided that you follow the rules of this License for verbatim copying of each of the documents in all other respects.

You may extract a single document from such a collection, and distribute it individually under this License, provided you insert a copy of this License into the extracted document, and follow this License in all other respects regarding verbatim copying of that document.

7. AGGREGATION WITH INDEPENDENT WORKS

A compilation of the Document or its derivatives with other separate and independent documents or works, in or on a volume of a storage or distribution medium, is called an "aggregate" if the copyright resulting from the compilation is not used to limit the legal rights of the compilation's users beyond what the individual works permit. When the Document is included in an aggregate, this License does not apply to the other works in the aggregate which are not themselves derivative works of the Document.

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8. TRANSLATION

Translation is considered a kind of modification, so you may distribute translations of the Document under the terms of section 4. Replacing Invariant Sections with translations requires special permission from their copyright holders, but you may include translations of some or all Invariant Sections in addition to the original versions of these Invariant Sections. You may include a translation of this License, and all the license notices in the Document, and any Warranty Disclaimers, provided that you also include the original English version of this License and the original versions of those notices and disclaimers. In case of a disagreement between the translation and the original version of this License or a notice or disclaimer, the original version will prevail.

If a section in the Document is Entitled "Acknowledgements", "Dedications", or "History", the requirement (section 4) to Preserve its Title (section 1) will typically require changing the actual title.

9. TERMINATION

You may not copy, modify, sublicense, or distribute the Document except as expressly provided for under this License. Any other attempt to copy, modify, sublicense or distribute the Document is void, and will automatically terminate your rights under this License. However, parties who have received copies, or rights, from you under this License will not have their licenses terminated so long as such parties remain in full compliance.

10. FUTURE REVISIONS OF THIS LICENSE

The Free Software Foundation may publish new, revised versions of the GNU Free Documentation License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. See http://www.gnu.org/copyleft/.

Each version of the License is given a distinguishing version number. If the Document specifies that a particular numbered version of this License "or any later version" applies to it, you have the option of following the terms and conditions either of that specified version or of any later version that has been published (not as a draft) by the Free Software Foundation. If the Document does not specify a version number of this License, you may choose any version ever published (not as a draft) by the Free Software Foundation.

INDEX

A

ADSL	20

alias	64

append	50

atime	50

B

bg	85

bootloaders

/boot/boot.b	31

/etc/lilo.conf	32

/sbin/lilo	32

1024 cylinder limit	36

1024 cylinders	32

bootloader	31

GRUB	32

grub shell	32

grub-install	32

grub.conf	32

LILO	31

C

cat	91

cd	72

chattr	49

chgrp	46

chmod	46

chown	46

chroot	4

compound commands

command1 && command2	64

command1 || command2	64

command1; command2	64

compress	50

configure	107p.

cp	74

Ctrl Z	85

cut	94

D

dd	2, 76

Debian	113

debugfs	43

df	45

dirsync	50

DISPLAY	139

display manager	140

display managers

gdm.conf	141

kdmrc	141

Xaccess	142

xdm-config	141, 142

Xrescources	142

Xservers	142

DMA	11

dmesg	11

dpkg	113

du	45

dump	50

dumpe2fs	43

E

e2fsck	43

echo	57

egrep	122, 123

env	58

eregex

?	122

+	122

|	122

exec	64

expand	93

export	58

ext3	50

F

fdisk	31

fg	85

fgrep	123

File Attributes	49

file globbing	67

files

/dev/ttyS0	17

/dev/ttyS1	17

/dev/ttyS2	17

/etc/isapnp.conf	12

/etc/ld.so.conf	104

/etc/mtab	45

/etc/updatedb.conf	73

/proc/dma	11

/proc/interrupts	11

/proc/ioports	11

/proc/mounts	45

/proc/pci	11

/var/log/dmesg	11

isapnp.conf	12

filesystem

absolute path	72

data blocks	42

ext2	42

ext3	42

inodes	42

permissions	46

relative path	72

superblock	42

filesystem hierarchy (FHS)

base directories	41

essential root (/) subdirectories	40

find	72

fips	2

fmt	95

fsck	43

fsck.ext2	43

fstab	33

fstab options

grpquota	34

noauto	34

owner	34

rw,ro	34

user	34

users	34

usrquota	34

G

gdm	141

grep	122, 123

H

head	92

hexdump	93

history	63

hotplug	13

I

I/O address	11

immutable	50

IRQs	11

isapnp	12

isapnptools	12

ISDN	20

isdn4k-utils	20

J

jobs	86

join	95

K

kdm	141

kill	83

kill signals

SIGHUP,SIGINT,SIGKILL.SIGTERM	83

killall	84

L

LD_LIBRARY_PATH	104

ldconfig	103

ldd	103

ln	75

locate	73

ls	73

lsattr	49

lspci	11

lsusb	13

M

make	108

Makefile	101, 107

man	65

Manpages	65

MANPATH	66

MBR	31

Metacharacters

command substitions

` command`	63

$(command)	63

file globbing,	62

quotes

``	63

' '	62

" "	62

range

[ ]	62

{string1,string2}	62

wildcards

?	62

*	62

mkdir	74

mke2fs	42

mkfs	42

mkfs.ext2	42

modem	17, 93, 165

mount	33, 45

mv	75

N

network cards	15

nice	84

nl	93

nohup	86

O

od	93

Orlov block allocator	50, 52

P

partitioning scheme	5

Partitions

extended	28

logical	28

mounting	33

naming convention	28

primary partition	28

root (/)	40

unmounting	34

paste	95

PID	82

pnpdump	12

PPPoE	20

pr	96

ps	82

pstree	82

pwd	72

Q

quotas

/etc/fstab	35

aquota.user	35

edquota	35

grace	35

quota	35

quotacheck	35

quotaon	35

quotastats	35

repquota	35

usrquota	35

R

rawrite	2

redirection and pipes

<	60

<<	64

>	60

>>	60

|	61

2>	61

2>&1	61

tee	62

regex

^	122

.	122

*t	122

\<	122

$	122

renice	85

rescue mode	4

resource allocation	11

rm	74

root (/)	5

rpm

major mode	109

minor mode	109

package integrity	111

package names	109

package signatures	110

query modes	109p.

S

SCSI

/proc/devices	28

/proc/scsi/scsi	15

booting	15

Channel	14

Device ID	14

LUN	14

SCSI ID	14

scsi_info	15, 26

sed	124

set	58

setting up modems	16

/dev/modem	18

COM1	17

COM2	17

COM3	17

setserial	17

wvdial	18

SGID	49

sndconfig	22

sort	95

split	93

startx	140

stderr	59

stdin	59

stdout	59

sticky bit	49

SUID	48

sync	50

synchronous	50

system-config-network	20

T

tac	91

tail	92

tail-merging	51

tee	62

top	83

touch	76

tr	96

tune2fs	34

U

umask	47

umount	34

undeletion	51

unexpand	93

uniq	94

updatedb	73

USB

/etc/hotplug	13

/etc/usbmgr/	14

EHCI ehci-hdc.o	13

OHCI usb-ohci.o	13

UHCI usb-uhci.o	13

usb.agent	14

usb.usermap	14

usbmgr	14

usbmodules	26

USB Support	13

V

vi

^,$,1G,G	130

:!	132

:quit,:q!,:wq,:exit,:x,:e,ZZ	132

/,?	131

a,A,i,o,O,s,S	130

b,e,),},w	129

c,r	130

d,dd,x,p	130

h,j,k,l	129

u,^R (undo, redo)	132

y	131

W

wc	92

whatis	65

whereis	73

which	73

winmodems	19

X

xauth	140

Xclients	140

Xdefaults	136

Xdefaults	139

xdm	141

xdm	140

xf86config	137

XF86Config	136p., 138

XF86Setup	137

xhost	139

xinit	140

xinitrc	140

Xresources	136, 139

Xsession	140

xvidtune	137

Z

zombie	145

LinuxIT Technical Training Centre

Installation
__________________________________________________

____________________________________________________________________________________________________________

Page 171

Hardware Configuration
____________________________________________________________________

_______________________________________________________________________________________________________

Managing Devices
______________________________________________________________

____________________________________________________________________________________________

The Linux Filesystem
_________________________________________________________________________

___________________________________________________________________________________________________________

The Command Line
____________________________________________________________________

______________________________________________________________________________________________________

File Management
________________________________________________________________________

________________________________________________________________________

Process Management
________________________________________________________________________

Text Processing
________________________________________________________________________

Software Installation
________________________________________________________________________

Advanced Text Manipulation
____________________________________________________________________

__________________________________________________________________

Using vi
___________________________________________________________________

______________________________________________________

The X Environment
____________________________________________________________________

_____________________________________________________________________________

Slides
_______________________________________________________________________________

_______________________________________________________________________________

All original materials are ©2003 LinuxIT. All Rights Reserved. Kleesh Consultants Ltd T/A LinuxIT registered in England No:04470427. Visit www.linuxit.com for more information.

Appendix
_______________________________________________________________________

GNU FDL License Agreement
________________________________________________________________________

License
________________________________________________________________________

Contents
__________________________________________________

___________________________________________________________________

LPI 101 Objectives
____________________________________________________________________

______________________________________________________________________________________________

Index
______________________________________________________

Hardware Configuration
________________________________________________

________________________________________________________________________________________________________

Managing Devices
____________________________________________

__________________________________________________________________________________________________

The Linux Filesystem
_________________________________________________

The Command Line
_______________________________________________

File Management
_________________________________________________

________________________________________________________________________________________

Process Management
_________________________________________________

Text Processing
_________________________________________________

Advanced Text Manipulation
______________________________________________

_____________________________________________________________________________________

Using vi
______________________________________________

The X Environment
______________________________________________

Answers to Review Questions
______________________________________________

Software Installation
_________________________________________________

LPI 101 RPM

Linux System Administration

none

2003-05-09T11:29:00

Adrian Thomasset