My 12.04 system wants to run a partial upgrade, as part of which it proposes to remove certain MariaDB packages (see screenshot below). Attached is my sources.list file - I don't understand why the system should be proposing the removal of the MariaDB packages, given I have explicitly chosen MariaDB as a replacement for MySQL?

clive@cooler-master:~$ cat /etc/apt/sources.list

# deb cdrom:[Ubuntu 12.04 LTS _Precise Pangolin_ - Release i386 (20120423)]/ precise main restricted



# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to

# newer versions of the distribution.

deb http://gb.archive.ubuntu.com/ubuntu/ precise main restricted

deb-src http://gb.archive.ubuntu.com/ubuntu/ precise main restricted



## Major bug fix updates produced after the final release of the

## distribution.

deb http://gb.archive.ubuntu.com/ubuntu/ precise-updates main restricted

deb-src http://gb.archive.ubuntu.com/ubuntu/ precise-updates main restricted



## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu

## team. Also, please note that software in universe WILL NOT receive any

## review or updates from the Ubuntu security team.

deb http://gb.archive.ubuntu.com/ubuntu/ precise universe

deb-src http://gb.archive.ubuntu.com/ubuntu/ precise universe

deb http://gb.archive.ubuntu.com/ubuntu/ precise-updates universe

deb-src http://gb.archive.ubuntu.com/ubuntu/ precise-updates universe



## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu 

## team, and may not be under a free licence. Please satisfy yourself as to 

## your rights to use the software. Also, please note that software in 

## multiverse WILL NOT receive any review or updates from the Ubuntu

## security team.

deb http://gb.archive.ubuntu.com/ubuntu/ precise multiverse

deb-src http://gb.archive.ubuntu.com/ubuntu/ precise multiverse

deb http://gb.archive.ubuntu.com/ubuntu/ precise-updates multiverse

deb-src http://gb.archive.ubuntu.com/ubuntu/ precise-updates multiverse



## N.B. software from this repository may not have been tested as

## extensively as that contained in the main release, although it includes

## newer versions of some applications which may provide useful features.

## Also, please note that software in backports WILL NOT receive any review

## or updates from the Ubuntu security team.

deb http://gb.archive.ubuntu.com/ubuntu/ precise-backports main restricted universe multiverse

deb-src http://gb.archive.ubuntu.com/ubuntu/ precise-backports main restricted universe multiverse



deb http://security.ubuntu.com/ubuntu precise-security main restricted

deb-src http://security.ubuntu.com/ubuntu precise-security main restricted

deb http://security.ubuntu.com/ubuntu precise-security universe

deb-src http://security.ubuntu.com/ubuntu precise-security universe

deb http://security.ubuntu.com/ubuntu precise-security multiverse

deb-src http://security.ubuntu.com/ubuntu precise-security multiverse



## Uncomment the following two lines to add software from Canonical's

## 'partner' repository.

## This software is not part of Ubuntu, but is offered by Canonical and the

## respective vendors as a service to Ubuntu users.

deb http://archive.canonical.com/ubuntu precise partner

# deb-src http://archive.canonical.com/ubuntu precise partner



## This software is not part of Ubuntu, but is offered by third-party

## developers who want to ship their latest software.

deb http://extras.ubuntu.com/ubuntu precise main

deb-src http://extras.ubuntu.com/ubuntu precise main



# MariaDB 5.5 repository list - created 2012-09-21 09:23 UTC

# http://downloads.mariadb.org/mariadb/repositories/

deb http://ftp.heanet.ie/mirrors/mariadb/repo/5.5/ubuntu precise main

deb-src http://ftp.heanet.ie/mirrors/mariadb/repo/5.5/ubuntu precise main



# deb http://repository.spotify.com stable non-free



deb http://deb.opera.com/opera/ stable non-free



deb http://ppa.launchpad.net/yorba/ppa/ubuntu precise main

deb-src http://ppa.launchpad.net/yorba/ppa/ubuntu precise main