A Short Introduction To Apt-Pinning
Version 1.0
Author: Falko Timme
This article is a short overview of how to use apt-pinning on Debian and Debian-based distributions (like Ubuntu). Apt-Pinning allows you to use multiple releases (e.g. stable, testing, and unstable) on your system and to specify when to install a package from which release. That way you can run a system based mostly on the stable release, but also install some newer packages from testing or unstable (or third-party repositories).
I do not issue any guarantee that this will work for you!
1 Preliminary Note
I'm using a Debian Lenny (stable) system here. I will explain apt-pinning on the basis of the package phpmyadmin which is available in three different versions in the stable, testing, and unstable repositories (at the time of this writing) - see http://packages.debian.org/search?keywords=phpmyadmin&searchon=names&suite=all§ion=all:
- lenny (stable): version 4:2.11.8.1-5
- squeeze (testing): version 4:3.1.2-2
- sid (unstable): version 4:3.1.3-1
2 My sources.list
I add the testing and unstable repositories to my /etc/apt/sources.list so that it looks as follows:
vi /etc/apt/sources.list
deb http://volatile.debian.org/debian-volatile lenny/volatile main deb-src http://volatile.debian.org/debian-volatile lenny/volatile main ## Lenny / Stable deb http://ftp2.de.debian.org/debian/ lenny main deb-src http://ftp2.de.debian.org/debian/ lenny main deb http://security.debian.org/ lenny/updates main deb-src http://security.debian.org/ lenny/updates main ## Squeeze / Testing deb http://ftp2.de.debian.org/debian/ squeeze main deb-src http://ftp2.de.debian.org/debian/ squeeze main deb http://security.debian.org/ squeeze/updates main deb-src http://security.debian.org/ squeeze/updates main ## Sid / Unstable deb http://ftp2.de.debian.org/debian/ sid main deb-src http://ftp2.de.debian.org/debian/ sid main |
Open /etc/apt/apt.conf...
vi /etc/apt/apt.conf
... and put the following line into it:
APT::Cache-Limit "100000000"; |
(Otherwise you might get an error like this one when running apt-get update:
E: Dynamic MMap ran out of room
)
Then run
apt-get update
to update the package database.
With the current version, apt would always try to install the newest version of a package which usually comes from unstable or testing - this could lead to a messed-up system. With apt-pinning, we can define priorities so that a package gets installed from unstable or testing only if there's no such package from stable.
We can check apt priorities as follows:
apt-cache policy
server1:~# apt-cache policy
Package files:
100 /var/lib/dpkg/status
release a=now
500 http://volatile.debian.org lenny/volatile/main Packages
release o=volatile.debian.org,a=stable,l=debian-volatile,c=main
origin volatile.debian.org
500 http://ftp2.de.debian.org sid/main Packages
release o=Debian,a=unstable,l=Debian,c=main
origin ftp2.de.debian.org
500 http://security.debian.org squeeze/updates/main Packages
release v=None,o=Debian,a=testing,l=Debian-Security,c=main
origin security.debian.org
500 http://ftp2.de.debian.org squeeze/main Packages
release o=Debian,a=testing,l=Debian,c=main
origin ftp2.de.debian.org
500 http://security.debian.org lenny/updates/main Packages
release v=5.0,o=Debian,a=stable,l=Debian-Security,c=main
origin security.debian.org
500 http://ftp2.de.debian.org lenny/main Packages
release v=5.0,o=Debian,a=stable,l=Debian,c=main
origin ftp2.de.debian.org
Pinned packages:
server1:~#
As you see, stable, testing, and unstable all have the same priority (500) which means that the newest version of a package would be installed. In the case of our phpmyadmin package this is version 4:3.1.3-1 which is from unstable:
apt-cache policy phpmyadmin
The Candidate: line shows the version that would be installed:
server1:~# apt-cache policy phpmyadmin
phpmyadmin:
Installed: (none)
Candidate: 4:3.1.3-1
Version table:
4:3.1.3-1 0
500 http://ftp2.de.debian.org sid/main Packages
4:3.1.2-2 0
500 http://ftp2.de.debian.org squeeze/main Packages
4:2.11.8.1-5 0
500 http://ftp2.de.debian.org lenny/main Packages
server1:~#
This is how priorities are defined (see
man 5 apt_preferences
):
P > 1000
causes a version to be installed even if this constitutes a downgrade of the package
990 < P <=1000
causes a version to be installed even if it does not come from the target release, unless the installed version is more recent
500 < P <=990
causes a version to be installed unless there is a version available belonging to the target release or the installed version is more recent
100 < P <=500
causes a version to be installed unless there is a version available belonging to some other distribution or the installed version is more recent
0 < P <=100
causes a version to be installed only if there is no installed version of the package
P < 0
prevents the version from being installed
