Re: postrm::downgrade?

[Andreas Metzler <ametzler@logic.univie.ac.at>]

On Wed, Jul 02, 2003 at 03:18:36PM +0800, Niall Young wrote:
> I'm aware you can downgrade packages with
>     `apt-get --force-yes install package=version-revision`
> but this doesn't seem to apply any postrm processing on the existing
> version of the package being replaced.
> 
> How about a postrm::downgrade hook to reverse any changes made in the
> new version's preinst::upgrade so that when the old version's preinst::upgrade
> is applied you're not left with a potential mix of configuration?
> 
> I'm using a custom package pool for deploying software, but we need to
> cleanly rollback if an upgrade doesn't go as expected.  Removing the
> package entirely and reinstalling isn't an option, it needs to be done
> seamlessly - i.e. reverse all changes made in the upgrade.  Is there
> another way?

You'd need more than that. Apt would need to be changed to handle
undoing of package splitting (Conflicts/Replaces), and is not always
possible anyway, new packages, might use new file-formats which can be
converted from the old-version but not back again.
             cu andreas