ee46e2f9b7
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
pip-and-virtualenv
This element installs pip and virtualenv in the image.
Note
This element setups and Python 2 and Python 3 environment. This means it will bring in python2 packages, so isn't appropriate if you want a python3 only environment.
Package install
If the package installtype is used then these programs are installed
from distribution packages. In this case, pip and
virtualenv will be installed only for the python
version identified by dib-python (i.e. the default python
for the platform).
Distribution packages have worked out name-spacing such that only
python2 or python3 owns common scripts like /usr/bin/pip
(on most platforms, pip refers to python2 pip, and
pip3 refers to python3 pip, although some may choose the
reverse).
To install pip and virtualenv from package:
export DIB_INSTALLTYPE_pip_and_virtualenv=packageSource install
Source install is the default. If the source installtype is used,
pip and virtualenv are installed from the
latest upstream releases.
Source installs from these tools are not name-spaced. It is
inconsistent across platforms if the first or last install gets to own
common scripts like /usr/bin/pip and
virtualenv.
To avoid inconsistency, we firstly install the packaged python 2
and 3 versions of pip and
virtualenv. This prevents a later install of these
distribution packages conflicting with the source install. We then
overwrite pip and virtualenv via
get-pip.py and pip respectively.
The system will be left in the following state:
/usr/bin/pip: python2 pip/usr/bin/pip2: python2 pip (same as prior)/usr/bin/pip3: python3 pip/usr/bin/virtualenv: python2 virtualenv
(note python3 virtualenv script is not
installed, see below)
Source install is supported on limited platforms. See the code, but this includes Ubuntu and RedHat platforms.
Using the tools
Due to the essentially unsolvable problem of "who owns the script",
it is recommended to not call pip or
virtualenv directly. You can directly call them with the
-m argument to the python interpreter you wish to install
with.
For example, to create a python3 environment do:
# python3 -m virtualenv myenv
# myenv/bin/pip install mytoolTo install a python2 tool from pip:
# python2 -m pip install mytoolIn this way, you can always know which interpreter is being used (and affected by) the call.
Ordering
Any element that uses these commands must be designated as 05-* or higher to ensure that they are first installed.