[Debconf-devel] Bug#908001: Removal of currently running kernel is prevented by "Failed to substitute package name in title: ..."

[Ben Hutchings]

Control: retitle -1 debconf: Fails to populate template cache during package removal
Control: reassign -1 src:debconf
Control: affects -1 linux-base

On Wed, 2018-09-05 at 03:00 +0200, Lars Kruse wrote:
> Package: linux-base
> Version: 4.5
> Severity: normal
> 
> Dear Maintainer,
> 
> I recently encountered the following situation while trying to remove the
> package of a currently running kernel:
> 
> root at router-foo:~# apt purge linux-image-4.9.0-6-amd64
> Reading package lists... Done
> Building dependency tree
> Reading state information... Done
> The following packages will be REMOVED:
>   linux-image-4.9.0-6-amd64*
> 0 upgraded, 0 newly installed, 1 to remove and 24 not upgraded.
> After this operation, 193 MB disk space will be freed.
> Do you want to continue? [Y/n]
> (Reading database ... 50646 files and directories currently installed.)
> Removing linux-image-4.9.0-6-amd64 (4.9.88-1+deb9u1) ...
> Failed to substitute package name in title: 10 at /usr/bin/linux-check-removal
> line 102, <STDIN> line 1. dpkg: error processing package
> linux-image-4.9.0-6-amd64 (--remove): subprocess installed pre-removal script
> returned error exit status 255 Errors were encountered while processing:
>  linux-image-4.9.0-6-amd64
> E: Sub-process /usr/bin/dpkg returned an error code (1)
[...]
> The only specific detail of the problematic environment is probably the
> fact, that /var/cache is stored on a tmpfs and thus is regularly
> discarded on every reboot.
[...]

This is an unusual configuration, but apparently valid (according to
the FHS).

Currently debconf only populates the cache during package installation
and in dpkg-reconfigure.  This means that asking any questions during
package removal has the same problem.  I verified that the same failure
occurs when attempting to remove an old kernel package that has a
similar prompt using its own template.

I think debconf should populate the cache from package template files
on-demand, using the first part of the template name as the package
name.

Ben.

-- 
Ben Hutchings
I'm always amazed by the number of people who take up solipsism because
they heard someone else explain it. - E*Borg on alt.fan.pratchett


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