apt wants to downgrade packages with pin-priority less than 1000

[Alon Swartz]

Binary package hint: apt

== Summary ==

apt will attempt to downgrade an installed package if the pin-priority of the package is greater than 99.

apt will not downgrade when pin-priorty is 99 or below because the already installed package automatically gets a priority of 100.

According to the apt_preferences manpage (mentioned several times), apt will *never* downgrade a package unless the priority of an available version exceeds 1000.

== Details ==

My testing system:
    Ubuntu 8.04.1 (Hardy)
    apt 0.7.9ubuntu17.1 for i386 compiled on Oct 27 2008 18:11:08

Reproducing the issue is simple, as described below (I have chosen base-files as its a small package without any build-deps, but any package will do).

# dpkg -s base-files |grep Version
Version: 4.0.1ubuntu5.8.04.3

# grep deb-src /etc/apt/sources.list.d/sources.list
deb-src http://archive.ubuntu.com/ubuntu hardy-updates main

# apt-get source base-files
dpkg-source: extracting base-files in base-files-4.0.1ubuntu5.8.04.3
dpkg-source: unpacking base-files_4.0.1ubuntu5.8.04.3.tar.gz

# head debian/changelog
base-files (4.0.1ubuntu5.8.04.3-1) hardy-proposed; urgency=low

  * testing pinning issue

 -- Alon Swartz <email address hidden> Tue, 06 Jan 2009 00:00:00 +0000

# dpkg-buildpackage -b -tc

# dpkg -i base-files_4.0.1ubuntu5.8.04.3-1_i386.deb
Setting up base-files (4.0.1ubuntu5.8.04.3-1) ...

# dpkg -s base-files |grep Version
Version: 4.0.1ubuntu5.8.04.3-1

# cat > /etc/apt/preferences <<EOF
Package: base-files
Pin: release o=Ubuntu
Pin-Priority: 999
EOF

Note: the pin-priority can be anything larger than 99 to reproduce this

# apt-cache policy base-files
base-files:
  Installed: 4.0.1ubuntu5.8.04.3-1
  Candidate: 4.0.1ubuntu5.8.04.3
  Package pin: 4.0.1ubuntu5.8.04.3
  Version table:
 *** 4.0.1ubuntu5.8.04.3-1 999
        100 /var/lib/dpkg/status
     4.0.1ubuntu5.8.04.3 999
        500 http://archive.ubuntu.com hardy-updates/main Packages
     4.0.1ubuntu5 999
        500 http://archive.ubuntu.com hardy/main Packages

# apt-get install base-files
The following packages will be DOWNGRADED:
  base-files

In other words, apt wants to downgrade a package even though the pin-priority is less than 1000, which goes against all the
documentation.

Is this a bug in apt, a bug in the documentation, or am I mis-understanding something?

[Max Bowsher (maxb)]

That's an interestingly weird bug. Confirmed on karmic (apt 0.7.21ubuntu1).

It is specific to using a "Package: name" pin. A "Package: *" pin does not reproduce the bug.

[Alon Swartz (alonswartz)]

"Package: name*" also does not reproduce the bug, but ofcourse will have the side effect of
pinning any package that matches name*

[Alon Swartz (alonswartz)]

I have just reproduced this issue on squeeze, and will be submitting a bug report to debian.

[Alon Swartz (alonswartz)]

Submitted to Debian:
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=543966

[Rolf Leggewie (r0lf)]

"Package: name*" will not work as expected. It is either an all-out wildcard * or the complete package name: http://bugs.debian.org/121132

[Rolf Leggewie (r0lf)]

actually, as confirmed in comment 1 and 2, what you guys are seeing is better described in bug 565364