Bug#711925: apache2-doc's config file breaks apache itself

[Stefan Fritsch <sf@sfritsch.de>]

Am Mittwoch, 24. Juli 2013, 21:37:18 schrieb Vincent Lefevre:
> dpkg: apache2.2-common: dependency problems, but removing anyway as
> you requested:
> 
>  apache2-mpm-worker depends on apache2.2-common (= 2.2.22-13).
> 
>  apache2 depends on apache2.2-common (= 2.2.22-13).
> 

...

> 
> Removing apache2.2-common ...
> 
> Purging configuration files for apache2.2-common ...

This is the problem. You have used --purge-unused (with aptitude) or 
--purge (with apt-get) while upgrading. Or the respective config 
options have been set in the apt/aptitude configuration files. This 
won't work and we will document that in the release notes. It will 
delete your old configuration (which is in apache2.2-common) before 
the new apache2 with the new configuration and the upgrade logic is 
installed. The aptitude man page clearly states the dangers of this 
option, but unfortunately the apt-get man page doesn't.

The bug in apache2 is that we still treat this situation as an upgrade 
in the postinst even if there is nothing left of the old install. If 
we can detect it, we should probably treat it as a new install 
instead.

This means the simple remedy to get things fixed is to purge the 
apache2 package and then re-install it. If removing apache2 causes 
other packages to be removed, be sure to NOT use the purge option 
mentioned above, or the other packages' configuration will be deleted, 
too. After apache2 is re-installed, re-install the reverse 
dependencies. In principle purging apache2 shouldn't delete anything 
valuable, because that has already been deleted when purging 
apache2.2-common. But I still recommend to make a backup, first.