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Re: Backup package and dpkg (was Re: dpkg-disappear-replace.txt)

Raul Miller:
   > If I understand correctly, there's an order imposed on package
   > installation by this feature.  To use dpkg installation to
   > recover a system, there would need to be some record of this
   > order.

Ian Jackson:

   However, I don't think this is a problem.  The feature's intended
   use is to allow various kinds of upgrade to happen, not as a way of
   deciding which packages provide certain files.

   It is only intended to come into play when an older package is
   superseded by one or more newer ones, and so it will be obvious
   what the ordering is - in fact, it will be impossible to install
   the packages in the wrong order because the old package won't exist
   any more.

Hmm... I agree that this feature's intended use was to allow certain
kinds of upgrades to happen.  However, I think I disagree with the
rest of this stuff.

Let me say, first off, that there exist plenty of useful systems which
are years behind on upgrades because reconfiguration to take advantage
of the upgrades is too painful/expensive to deal with.

Secondly, there exist a variety of distribution mechanisms
(e.g. cd-roms) where the older package will be available.

Now, obviously, it would be the responsibility of the backup system
and backup administrator to track the storage of backup information --
including where the proper .deb files are kept.  However, if we accept
that the backup system is going to try and do a real system restore
by providing a superstructure over the dpkg system, I think that
constitutes a need for dpkg to track and export package installation

Also, as an aside, I don't think it's fair to rely on dpkg to recover
packages which aren't in a fully installed state -- so it should be
the responsibility of the backup system to (a) issue big warnings if
it's backing up a system with installed but unconfigured packages, and
(b) backup all files from such packages by default.


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