Частичное обновление - зачем удалять MariaDB?

Моя система 12.04 хочет запустить частичное обновление, в рамках которого она предлагает удалить определенные пакеты MariaDB (см. Скриншот ниже). В приложении находится мой sources.list файл - я не понимаю, почему система должна предлагать удаление пакетов MariaDB, учитывая, что я явно выбрал MariaDB вместо 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