Re: image-postproc-extension.bbclass modifying /etc/os-release

[Henning Schild <henning.schild@siemens.com>]

Am Fri, 15 Jan 2021 15:26:14 +0100
schrieb "[ext] Silvano Cirujano Cuesta"
<silvano.cirujano-cuesta@siemens.com>:

> Hi,
> 
> I've noticed that '/etc/os-release' is being changed on the image in
> meta/classes/image-postproc-extension.bbclass [1].  What BTW ends up
> changing '/usr/lib/os-release', since it's only a symlink. But both
> '/etc/os-release' and '/usr/lib/os-release' are owned by
> 'base-files'...
> 
> An upgrade of 'base-files' would be replacing (silently, since is not
> marked as a configuration file) '/usr/lib/os-release' with the
> version of the upstream 'base-files' package and possibly breaking
> any tools in the system relying on certain values in that file.

We found that we can not even place a file in /etc/ it will always be
replaced with that symlink, no config file protection on this one.
While we could talk with upstream about that violation, we would also
need a way of dealing with it, because it is unlikely to change in
stable distros. 

> Is there a reason that I'm missing for doing so instead of the
> Debian-way (file diversion with dpkg-divert)? Or any hack that I've
> overseen that avoids the mentioned breakage?

So i propose a hack as follows:

- write a script that can create /etc/os-release from a given default
  and a second file /etc/os-release-isar
  - if variable in both, prefer isar
  - if variable only in isar, append
  - if variable only in original, use
- put that script into a package we install in every isar image
- place a dpkg or apt hook into that package
  - test -f /etc/os-release-isar && test -h /etc/os-release
- create/change /etc/os-release-isar in image postproc and run hook 

Henning

> Hasta la vista,
> 
>   Silvano
> 
> [1]
> https://github.com/ilbers/isar/blob/a0d6de4ac7dfb926b38cfcd44f2bc8852f2e43e3/meta/classes/image-postproc-extension.bbclass#L20
>