purging /var/cache breaks debconf

[Ben Howard]

If user deletes /var/cache/*, while leaving /var/cache, then debconf is broken. Specifically, debconf looks for /var/cache/debconf and does not create the missing directory, and after the directory is creating, software fails to install.

Repo Steps:
1. rm /var/cache/*
2. Attempt to install any package

Why this is a bug? Per the LSB, ( http://www.pathname.com/fhs/pub/fhs-2.3.html#VARCACHE), applications should recover from missing files. A user who removes /var/cache/* will experience problems with the installation of software.

root@domU-12-31-39-0B-60-05:/home/ubuntu# lsb_release -d
Description: Ubuntu oneiric (development branch)

root@domU-12-31-39-0B-60-05:/home/ubuntu# apt-cache policy debconf
debconf:
  Installed: 1.5.40ubuntu1
  Candidate: 1.5.40ubuntu1
  Version table:
 *** 1.5.40ubuntu1 0
        500 http://us-east-1.ec2.archive.ubuntu.com/ubuntu/ oneiric/main i386 Packages
        100 /var/lib/dpkg/status
root@domU-12-31-39-0B-60-05:/home/ubuntu#

---
Attempt to install the Sun JDK:

sun-dlj-v1-1 license could not be presented
try 'dpkg-reconfigure debconf' to select a frontend other than noninteractive

dpkg: error processing /var/cache/apt/archives/sun-java6-jre_6.26-1oneiric1_all.deb (--unpack):
 subprocess new pre-installation script returned error exit status 2
Unpacking sun-java6-bin (from .../sun-java6-bin_6.26-1oneiric1_i386.deb) ...

sun-dlj-v1-1 license could not be presented
try 'dpkg-reconfigure debconf' to select a frontend other than noninteractive

dpkg: error processing /var/cache/apt/archives/sun-java6-bin_6.26-1oneiric1_i386.deb (--unpack):
 subprocess new pre-installation script returned error exit status 2
Unpacking sun-java6-jdk (from .../sun-java6-jdk_6.26-1oneiric1_i386.deb) ...

sun-dlj-v1-1 license could not be presented
try 'dpkg-reconfigure debconf' to select a frontend other than noninteractive

ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: debconf 1.5.40ubuntu1
ProcVersionSignature: Ubuntu 3.0.0-7.9-virtual 3.0.0
Uname: Linux 3.0.0-7-virtual i686
Architecture: i386
Date: Tue Aug 2 18:16:15 2011
Ec2AMI: ami-d319dfba
Ec2AMIManifest: (unknown)
Ec2AvailabilityZone: us-east-1c
Ec2InstanceType: t1.micro
Ec2Kernel: aki-805ea7e9
Ec2Ramdisk: unavailable
PackageArchitecture: all
ProcEnviron:
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: debconf
UpgradeStatus: No upgrade log present (probably fresh install)

[Ben Howard (darkmuggle-deactivatedaccount)]

Example of a failed installation:

ubuntu@ip-10-112-41-194:~$ sudo apt-get install bzr
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following extra packages will be installed:
  bzrtools python-bzrlib
Suggested packages:
  bzr-doc bzr-gtk bzr-svn python-bzrlib.tests graphviz librsvg2-bin python-kerberos python-bzrlib-dbg xdg-utils
The following NEW packages will be installed:
  bzr bzrtools python-bzrlib
0 upgraded, 3 newly installed, 0 to remove and 0 not upgraded.
Need to get 1,981 kB of archives.
After this operation, 10.3 MB of additional disk space will be used.
Do you want to continue [Y/n]? y
Get:1 http://us-east-1.ec2.archive.ubuntu.com/ubuntu/ oneiric/main python-bzrlib i386 2.4.0~beta5-2ubuntu1 [1,887 kB]
Get:2 http://us-east-1.ec2.archive.ubuntu.com/ubuntu/ oneiric/main bzr all 2.4.0~beta5-2ubuntu1 [35.2 kB]
Get:3 http://us-east-1.ec2.archive.ubuntu.com/ubuntu/ oneiric/main bzrtools all 2.4.0~bzr767-2ubuntu1 [58.6 kB]
Fetched 1,981 kB in 0s (2,316 kB/s)
debconf: DbDriver "config": could not open /var/cache/debconf/config.dat
Selecting previously deselected package python-bzrlib.
(Reading database ... 27688 files and directories currently installed.)
Unpacking python-bzrlib (from .../python-bzrlib_2.4.0~beta5-2ubuntu1_i386.deb) ...
Selecting previously deselected package bzr.
Unpacking bzr (from .../bzr_2.4.0~beta5-2ubuntu1_all.deb) ...
Selecting previously deselected package bzrtools.
Unpacking bzrtools (from .../bzrtools_2.4.0~bzr767-2ubuntu1_all.deb) ...
Processing triggers for python-central ...
Processing triggers for man-db ...
debconf: DbDriver "config": could not open /var/cache/debconf/config.dat
dpkg: error processing man-db (--unpack):
 subprocess installed post-installation script returned error exit status 1
Errors were encountered while processing:
 man-db
E: Sub-process /usr/bin/dpkg returned an error code (1)

[Ben Howard (darkmuggle-deactivatedaccount)]

http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=636621

[dino99 (9d9)]

That version is no more maintained