Make a version-less RHEL element to handle both '7' and '8' DIB_RELEASE.
The element usage should align with other elements which operate in the
same way such as the Fedora element.
Additionally, this patch adds support for RHEL8 that operates with
Python 3.
As of now, users of diskimage-builder will still be able to use the
'rhel7' element, or migrate to 'rhel' and specify their respective
DIB_RELEASE value.
* mount the xfs file-system for extraction as read-only. vaguely
based on explaination in [1] and the fact we only read the image
data into a tar, so can ignore this.
XFS (dm-1): Superblock has unknown read-only compatible features (0x4) enabled.
* Use the redhat system python as the dib-python version. dib was
ahead of it's time making an abstracted python interpreter for
system work ;) the system python should work for running the various
dib element scripts.
[1] https://unix.stackexchange.com/questions/247550/unmountable-xfs-filesystem
Redhat-Bug: https://bugzilla.redhat.com/show_bug.cgi?id=1700253
Co-Authored-By: Ian Wienand <iwienand@redhat.com>
Change-Id: I90540675c70bb475d9db2ae24f81c648a31f3f95
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
