apt-get
is the first interface — command-line based — which was developed within the project.
synaptic
, aptitude
(which includes both a text mode interface and a graphical one — even if not complete yet), wajig
, etc. The most recommended interface, aptitude
, is the one used during the installation of Debian. Since its command-line syntax is very similar to apt-get
's, we will be focusing on aptitude
in the examples given in this section. When there are major differences between aptitude
and apt-get
, these differences will be detailed.
aptitude update
. Depending on the speed of your connection, the operation can take a while since it involves downloading a certain number of Packages.(gz|bz2)
files (or even Sources.(gz|bz2)
), which have gradually become bigger and bigger as Debian has developed (more than 8 MB for the largest Packages.gz
— from the main
section). Of course, installing from a CD-ROM set does not require any downloading — in this case, the operation is very fast.
aptitude install package
and aptitude remove package
. In both cases, APT will automatically install the necessary dependencies or delete the packages which depend on the package that is being removed. The aptitude purge package
or apt-get purge package
commands involve a complete uninstallation — the configuration files are also deleted.
sources.list
mentions several distributions, it is possible to give the version of the package to install. A specific version number can be requested with aptitude install package
=version
, but indicating its distribution of origin (Stable, Testing or Unstable) — with aptitude install package
/distribution
— is usually preferred. With this command, it is possible to go back to an older version of a package (if for instance you know that it works well), provided that it is still available in one of the sources referenced by the sources.list
file. Otherwise the snapshot.debian.org
archive can come to the rescue (see sidebar GOING FURTHER Old package versions: snapshot.debian.org
).
Example 6.2. Installation of the unstable version of spamassassin
#
aptitude install spamassassin/unstable
aptitude safe-upgrade
or apt-get upgrade
(of course after aptitude update
). This command looks for installed packages which can be upgraded without removing any packages. In other words, the goal is to ensure the least intrusive upgrade possible. apt-get
is slightly more demanding than aptitude
because it will refuse to install packages which were not installed beforehand.
aptitude
will generally select the most recent version number (except for Experimental packages, which are ignored by default whatever their version number). If you specified Testing or Unstable in your sources.list
, aptitude safe-upgrade
will switch most of your Stable system to Testing or Unstable, which might not be what you intended.
aptitude
to use a specific distribution when searching for upgraded packages, you need to use the option -t
or --target-release
, followed by the name of the distribution you want (for example: aptitude -t stable safe-upgrade
). To avoid specifying this option every time you use aptitude
, you can add APT::Default-Release "stable";
in the file /etc/apt/apt.conf.d/local
.
aptitude full-upgrade
(the option used to be named dist-upgrade
, for “distribution upgrade”). With this instruction, aptitude
will complete the upgrade even if it has to remove some obsolete packages or install new dependencies. This is also the command used by users who work daily with the Debian Unstable release and follow its evolution day by day. It is so simple that it hardly needs explanation: APT's reputation is based on this great functionality.
aptitude dist-upgrade
is still available as a synonym for aptitude full-upgrade
; apt-get
only recognizes the former.
/etc/apt/apt.conf.d/
directory. Remember for instance that it is possible for APT to tell dpkg
to ignore file conflict errors by specifying DPkg::Options { "--force-overwrite"; }
.
Acquire::http::proxy "http://yourproxy
:3128"
. For an FTP proxy, write Acquire::ftp::proxy "ftp://yourproxy
"
. To discover more configuration options, read the apt.conf(5) manual page with the command man apt.conf
(for details on manual pages, see next chapter).
-t
command-line option or the APT::Target-Release
configuration directive).
/etc/apt/preferences
with the names of the affected packages, their version, their origin and their new priority.
/etc/apt/preferences
, it first takes into account the most specific entries (often those specifying the concerned package), then the more generic ones (including for example all the packages of a distribution). If several generic entries exist, the first match is used. The available selection criteria include the package's name and the source providing it. Every package source is identified by the information contained in a Release
file that APT downloads together with the Packages.gz
files. It specifies the origin (usually “Debian” for the packages of official mirrors, but it can also be a person's or an organization's name for third-parties repositories). It also gives the name of the distribution (usually Stable, Testing, Unstable or Experimental for the standard distributions provided by Debian) together with its version (for example 5.0 for Debian Lenny). Let's have a look at its syntax through some realistic case studies of this mechanism.
/etc/apt/preferences
file:
Package: * Pin: release a=stable Pin-Priority: 900 Package: * Pin: release o=Debian Pin-Priority: -10
a=stable
defines the name of the selected distribution. o=Debian
limits the scope to packages whose origin is “Debian”.
Package: perl Pin: version 5.10* Pin-Priority: 1001
man apt_preferences
.
aptitude
being such a marvelous tool, it is tempting to pick packages coming from other distributions. For example, after having installed a Stable system, you might want to try out a software package available in Testing or Unstable without diverging too much from the system's initial state.
aptitude
manages such coexistence very well and limits risks very effectively. The best way to proceed is to list all distributions used in /etc/apt/sources.list
(some people always put the three distributions, but remember that Unstable is reserved for experienced users) and to define your reference distribution with the APT::Default-Release
parameter (see Section 6.2.3, “System Upgrade”).
sources.list
file. In this case, you can use aptitude install package
/testing
to install a package from Testing. If the installation fails due to some unsatisfiable dependencies, let it solve those dependencies within Testing by adding the -t testing
parameter. The same obviously applies to Unstable.
safe-upgrade
and dist-upgrade
) are done within Stable except for packages already upgraded to an other distribution: those will follow updates available in the other distributions. We'll explain this behavior with the help of the default priorities set by APT below. Do not hesitate to use apt-cache policy
(see sidebar) to verify the given priorities.
/etc/apt/preferences
has not been used to force priorities higher than 1000 for some packages).
/etc/apt/preferences
to this effect:
Package: * Pin: release a=unstable Pin-Priority: 490