diskimage-builder/diskimage_builder/elements/dpkg/README.rst
Ian Wienand 97c01e48ed Move elements & lib relative to diskimage_builder package
Currently we have all our elements and library files in a top-level
directory and install them into
<root>/share/diskimage-builder/[elements|lib] (where root is either /
or the root of a virtualenv).

The problem with this is that editable/development installs (pip -e)
do *not* install data_files.  Thus we have no canonical location to
look for elements -- leading to the various odd things we do such as a
whole bunch of guessing at the top of disk-image-create and having a
special test-loader in tests/test_elements.py so we can run python
unit tests on those elements that have it.

data_files is really the wrong thing to use for what are essentially
assets of the program.  data_files install works well for things like
config-files, init.d files or dropping documentation files.

By moving the elements under the diskimage_builder package, we always
know where they are relative to where we import from.  In fact,
pkg_resources has an api for this which we wrap in the new
diskimage_builder/paths.py helper [1].

We use this helper to find the correct path in the couple of places we
need to find the base-elements dir, and for the paths to import the
library shell functions.

Elements such as svc-map and pkg-map include python unit-tests, which
we do not need tests/test_elements.py to special-case load any more.
They just get found automatically by the normal subunit loader.

I have a follow-on change (I69ca3d26fede0506a6353c077c69f735c8d84d28)
to move disk-image-create to a regular python entry-point.

Unfortunately, this has to move to work with setuptools.  You'd think
a symlink under diskimage_builder/[elements|lib] would work, but it
doesn't.

[1] this API handles stuff like getting files out of .zip archive
modules, which we don't do.  Essentially for us it's returning
__file__.

Change-Id: I5e3e3c97f385b1a4ff2031a161a55b231895df5b
2016-11-01 17:27:41 -07:00

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====
dpkg
====
Provide dpkg specific image building glue.
The ubuntu element needs customisations at the start and end of the image build
process that do not apply to RPM distributions, such as using the host machine
HTTP proxy when installing packages. These customisations live here, where they
can be used by any dpkg based element.
The dpkg specific version of install-packages is also kept here.
Environment Variables
---------------------
DIB_APT_KEYS
:Required: No
:Default: None
:Description: If an extra or updated apt key is needed then define
``DIB_ADD_APT_KEYS`` with the path to a folder. Any key files inside will be
added to the key ring before any apt-get commands take place.
:Example: ``DIB_APT_KEYS=/etc/apt/trusted.gpg.d``
DIB_APT_LOCAL_CACHE
:Required: No
:Default: 1
:Description: By default the ``$DIB_IMAGE_CACHE/apt/$DISTRO_NAME`` directory is
mounted in ``/var/cache/apt/archives`` to cache the .deb files downloaded
during the image creation. Use this variable if you wish to disable the
internal cache of the ``/var/cache/apt/archives`` directory
:Example: ``DIB_APT_LOCAL_CACHE=0`` will disable internal caching.
DIB_DISABLE_APT_CLEANUP
:Required: No
:Default: 0
:Description: At the end of a dib run we clean the apt cache to keep the image
size as small as possible. Use this variable to prevent cleaning the apt cache
at the end of a dib run.
:Example: ``DIB_DISABLE_APT_CLEANUP=1`` will disable cleanup.