On Sat, Aug 23, 2008 at 10:43:17PM +0200, Sven Joachim wrote:
> > Well, it's an aptitude bug, so doing so. The dependencies of the old
> > version of the package *must* still be installed when the preinst of the new
> > package is being run, because the new-preinst is called by dpkg in the phase
> > when dpkg may still try to roll back to the old version on failure.
> Can you back up this statement with a reference in the policy manual?
> It seems that this may not always be possible, for instance when the old
> version of the upgraded package was not configured.
No, the current version of policy doesn't speak to this directly. Here is
the proof that this is a bug in aptitude:
- The old version of the package depends on the old library.
- Policy requires that Depends: are satisfied for a package to be in the
'configured' state.
- The prerm script is called before the package is deconfigured.
- Therefore, the package's dependencies must still be installed at the point
when the prerm script is called; removing the dependency first violates
the dependency relationship, and is a bug in whatever tool is doing this.
(N.B., dpkg itself does not enforce this when asked to remove dependencies
of already-configured packages; it's the responsibility of the front end
to get the order right.)
- On package upgrade, the preinst script of the new package is called
*before* the prerm of the old package.
- Therefore, the preinst is being called while the old version of the
package is still in "installed" state.
- Therefore, it is a bug in the package manager that the dependencies of
the old version of the package are not installed at the time the new
preinst is run.
> OTOH, I found the following statement in section 7.2:
> `Pre-Depends' are also required if the `preinst' script depends
> on the named package. It is best to avoid this situation if
> possible.
> It seems that this is just the situation here.
No, it is not. slapd does *not* have a dependency on obsolete and
no-longer-extant versions of the libldap library package; it only requires
that on upgrade, at the time the preinst runs, the old version of *slapd
itself* be in a consistent state.
This is standard practice in maintainer scripts.
> Compare also the discussion around #469552/#314571, especially your own
> statement in http://lists.debian.org/debian-devel/2008/07/msg01028.html.
If you don't understand the difference between these two cases, I fervently
hope that you aren't going anywhere near the package manager code.
--
Steve Langasek Give me a lever long enough and a Free OS
Debian Developer to set it on, and I can move the world.
Ubuntu Developer http://www.debian.org/
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