Step: copy-file
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Copy a file from outside into the target filesystem.

Step keys:

* `copy-file` &mdash; REQUIRED; the full (starting from the new
  filesystem root) path name of the file to create. Any missing
  directories will be created (owner root, group root, mode 0511).
* `src` &mdash; REQUIRED; filename on the host filesystem, outside the
  chroot, relative to the current working directory of the vmdb2
  process.
* `perm` &mdash; OPTIONAL; the numeric (octal) representation of the
  file's permissions. Defaults to 0644.
* `uid` &mdash; OPTIONAL; the numeric user ID of the file's
  owner. Defaults to 0 (root).
* `gid` &mdash; OPTIONAL; the numeric user ID of the file's
  group. Defaults to 0 (root).

