## catatonit ##

[![Build Status](https://travis-ci.org/openSUSE/catatonit.svg?branch=master)](https://travis-ci.org/openSUSE/catatonit)

A container init that is so simple it's effectively brain-dead. This is a
rewrite of [initrs][initrs] in C, because we found that it is not possible to
statically compile Rust binaries without using musl. That was, in turn, a
reimplementation of other container inits like `tini` and `dumb-init`.

The reason for re-implementing `docker-init` is because it appears as though
all of the other implementations do not handle signals as correctly as they
should. In particular, they all appear to make use of `sigwait(2)` (`tini` does
a `sigtimedwait(2)` for an interval and then will do a `waitpid(2)` even if it
didn't detect a `SIGCHLD`). `catatonit` uses `signalfd(2)`, which [has its own
warts][signalfd-broken], but the improvements over `sigwait(2)` are significant
in terms of stability. Ideally we would just write a patch for the other
projects to use `signalfd(2)` rather than creating a new project, but after
some time spent looking at `tini` and `dumb-init` we felt that such patches
would be closer to full rewrites.

In addition, the purpose of `catatonit` is to only support the key usage by
`docker-init` which is `/dev/init -- <your program>`. With few exceptions, no
other features will be added.

[initrs]: https://github.com/cyphar/initrs
[signalfd-broken]: https://ldpreload.com/blog/signalfd-is-useless

### Usage ###

catatonit has identical usage to other basic `docker-init`'s -- you give it the
command and list of arguments to that command. If catatonit is not pid1, it
will try to use the sub-reaper support in the kernel. You can pass `-g` if you
want signals to be forwarded to the entire process group of your spawned
process (otherwise it's just forwarded to the process spawned).

If you wish to use catatonit as a convenient pause container (do not spawn a
child process nor do any signal handling), use pass `-P`.

### Installation ###

catatonit uses autotools for building, so building is a fairly standard:

```
% ./autogen.sh
% ./configure
% make
% sudo make install
```

### License ###

catatonit is licensed under the GNU General Public License version 3 or later.

```
catatonit: a container init so simple it's effectively brain-dead
Copyright (C) 2018-2019 SUSE LLC

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <https://www.gnu.org/licenses/>.
```
