Apt-Pinning

Apt-Pinning is a method to set priorities on certain Debian/Ubuntu repos. This can be useful to make some experimental repos be excluded, but useful if you need a few packages from them.

Example: Lucid with some Maverick Packages

0. Run apt-get update; apt-get dist-upgrade to get completely up to date in pure lucid.

1. Setup maverick sources in your sources.list.d:

deb http://us.ubuntu.com/ubuntu/ maverick main restricted universe multiverse
deb-src http://us.ubuntu.com/ubuntu/ maverick main restricted universe multiverse

deb http://us.ubuntu.com/ubuntu/ maverick-updates main restricted universe multiverse
deb-src http://us.ubuntu.com/ubuntu/ maverick-updates main restricted universe multiverse

deb http://security.ubuntu.com/ubuntu maverick-security main restricted universe multiverse
deb-src http://security.ubuntu.com/ubuntu maverick-security main restricted universe multiverse

2. Run:

apt-get update

3. At this point if you did a dist-upgrade it would upgrade your box to maverick, which is not intended. Now you must pin your packages. Lets say you want wordpress but not everything else. Then put this in a file in /etc/apt/preferences.d/

Package: wordpress
Pin: release a=maverick
Pin-Priority: 800

Package: wordpress
Pin: release a=maverick-security
Pin-Priority: 800

Package: wordpress
Pin: release a=maverick-updates
Pin-Priority: 800

Package: *
Pin: release a=maverick
Pin-Priority: -1

Package: *
Pin: release a=maverick-security
Pin-Priority: -1

Package: *
Pin: release a=maverick-updates
Pin-Priority: -1

4. Run apt-cache policy wordpress to see what it wants to do with the wordpress package:

root@server:~# apt-cache policy wordpress
wordpress:
  Installed: (none)
  Candidate: 3.0.1-1ubuntu1.1
  Package pin: 3.0.1-1ubuntu1.1
  Version table:
     3.0.1-1ubuntu1.1 800
         -1 http://mirrors.tummy.com/pub/ftp.ubuntulinux.org/ubuntu/ maverick-updates/universe Packages
         -1 http://security.ubuntu.com/ubuntu/ maverick-security/universe Packages
     3.0.1-1ubuntu1 800
         -1 http://mirrors.tummy.com/pub/ftp.ubuntulinux.org/ubuntu/ maverick/universe Packages
     2.9.2-1ubuntu1.1 800
        500 http://mirrors.tummy.com/pub/ftp.ubuntulinux.org/ubuntu/ lucid-updates/universe Packages
        500 http://security.ubuntu.com/ubuntu/ lucid-security/universe Packages
     2.9.2-1ubuntu1 800
        500 http://mirrors.tummy.com/pub/ftp.ubuntulinux.org/ubuntu/ lucid/universe Packages

You can see it wants to install the new version from maverick.

5. Now run apt-cache policy bash to see what it wants to do with bash:

bash:
  Installed: 4.1-2ubuntu3
  Candidate: 4.1-2ubuntu3
  Version table:
     4.1-2ubuntu4 0
         -1 http://mirrors.tummy.com/pub/ftp.ubuntulinux.org/ubuntu/ maverick/main Packages
 *** 4.1-2ubuntu3 0
        500 http://mirrors.tummy.com/pub/ftp.ubuntulinux.org/ubuntu/ lucid/main Packages
        100 /var/lib/dpkg/status

You can see it doesn't want to upgrade bash

6. Run:

apt-get --dry-run dist-upgrade

It shouldn't try to upgrade anything

7. run

apt-get install wordpress

Should install wordpress from maverick