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

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  Bug#908001: Removal of currently running kernel is prevented by "Failed to substitute package name in title: ..." Lars Kruse <devel@sumpfralle.de> - 2018-09-05 03:10 +0200
    Processed: Re: Bug#908001: Removal of currently running kernel is  prevented by "Failed to substitute package name in title: ..." "Debian Bug Tracking System" <owner@bugs.debian.org> - 2018-09-05 20:10 +0200
    Bug#908001: Removal of currently running kernel is prevented by "Failed to substitute package name in title: ..." Ben Hutchings <ben@decadent.org.uk> - 2018-09-05 20:10 +0200

#61990 — Bug#908001: Removal of currently running kernel is prevented by "Failed to substitute package name in title: ..."

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@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)

Instead of the above error message I expected a dialog asking for
confirmation of the removal of the currently running kernel.

The same happens reproducible for many hosts (all sharing the same
setup).

Minimal test:
 /usr/share/debconf/frontend /usr/bin/linux-check-removal "$(uname -r)"

In case of success, the above command leads to a dialog asking for
confirmation for removing the currently running kernel.
In case of failure, the following error is emitted (resulting in an
exitcode 255):
 Failed to substitute package name in title: 10 at /usr/bin/linux-check-removal
line 102, <STDIN> line 1.

The problem can be fixed by executing
/var/lib/dpkg/info/linux-base.postinst.
This results (among others) in the following new section in
/var/cache/debconf/config.dat:

Name: linux-base/removing-running-kernel
Template: linux-base/removing-running-kernel
Value: true
Owners: linux-base
Flags: seen
Variables:
 running = 4.9.0-6-amd64

The problem returns, if the above section is removed from that file.

Thus it looks like the script "linux-check-removal" does not handle a
situation where the above debconf data is missing. This probably
involves very specific circumstances, since the linux-base is widely
used and seems to work well for most users.

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.

Cheers,
Lars

-- System Information:
Debian Release: 9.4
  APT prefers stable-updates
  APT policy: (500, 'stable-updates'), (500, 'stable')
Architecture: amd64 (x86_64)

Kernel: Linux 4.9.0-6-amd64 (SMP w/4 CPU cores)
Locale: LANG=de_DE.UTF-8, LC_CTYPE=de_DE.UTF-8 (charmap=UTF-8),
LANGUAGE=de_DE.UTF-8 (charmap=UTF-8) Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages linux-base depends on:
ii  debconf [debconf-2.0]  1.5.61

linux-base recommends no packages.

linux-base suggests no packages.

-- debconf information:
  linux-base/removing-title:
* linux-base/removing-running-kernel: true

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#62005 — Processed: Re: Bug#908001: Removal of currently running kernel is prevented by "Failed to substitute package name in title: ..."

Processing control commands:

> retitle -1 debconf: Fails to populate template cache during package removal
Bug #908001 [linux-base] Removal of currently running kernel is prevented by "Failed to substitute package name in title: ..."
Changed Bug title to 'debconf: Fails to populate template cache during package removal' from 'Removal of currently running kernel is prevented by "Failed to substitute package name in title: ..."'.
> reassign -1 src:debconf
Bug #908001 [linux-base] debconf: Fails to populate template cache during package removal
Bug reassigned from package 'linux-base' to 'src:debconf'.
No longer marked as found in versions linux-base/4.5.
Ignoring request to alter fixed versions of bug #908001 to the same values previously set
> affects -1 linux-base
Bug #908001 [src:debconf] debconf: Fails to populate template cache during package removal
Added indication that 908001 affects linux-base

-- 
908001: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=908001
Debian Bug Tracking System
Contact owner@bugs.debian.org with problems

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#62006

[Multipart message — attachments visible in raw view] — view raw

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@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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