Re: problems in upgrade
Anthony Towns <aj@azure.humbug.org.au> wrote:
> Aha! More importantly, there's the non-essential, but required and depended
> upon by perl (not perl-base) package libdb2, which doesn't Pre-Depend: on
> libc6.
Correct.
> I think what's happening is that:
> /usr/bin/perl (provided by perl-base.deb) is essential and must
> always work
Actually, it's perl-5.005-base in potato.
> when perl.deb is installed, /usr/bin/perl only works if libdb.so.3
> (provided by libdb2) works, which in turn only works with a new
> libc6. perl depends on libdb2 (not pre-depends), libdb2 depends on
> the new libc6 (not pre-depends).
libdb.so.3 is in potato as well, in libc6.
> Hrm. Further, libc6 Depends on libdb2, but doesn't Pre-Depend on it.
> Not sure what the correct fix here is.
> Perhaps:
> libc6 Depends: libdb2
> libdb2 Pre-Depends: libc6
> perl Pre-Depends: libdb2
This still doesn't prevent the reverse of the observed problem from
happening, i.e., the new libc6 gets unpacked first, and then some other
package gets unpacked before libdb2 is, in which case perl will be broken
for that duration since libc6 no longer provides libdb.so.3.
> ? Are Depends/Pre-Depends loops allowed, or are they as bad as Pre-Depends
> loops?
I don't see why this won't work, as pre-dependencies are considered to be
satisfied during unpacking if the package that is depended on has been
unpacked and has been configured successfully before. However, a
pre-depends loop will cause problems.
<rant>
Something that has been a pet peeve of mine for a long time: dpkg does not
deconfigure a package when upgrading its dependencies.
If we did that here, then this problem disappears. Since to unpack the new
libdb2, you have to deconfigure perl, which is essential. So this forces
you to configure libdb2 as soon as possible. The same thing applies when
you unpack the new libc6.
</rant>
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