The package management system binds all the software on a Debian system together. Debian uses named "packages" for each piece of software, bundles of files which provide the files to be installed on the system, the dependencies between packages and the configuration of the software. These packages can be installed or removed (unless, of course some other package requires it) at will. In fact, the majority of the Debian installation process is installing the most basic packages that allow Debian to function.
Debian package management consists of several layers. The lowest layers, most of which you won't want to touch, are made up of dpkg and associated programs. On top of those layers are the Apt and apt-get tools as well as the newer aptitude tool. The Package Management Tools page has brief descriptions of these and other tools which work with DebianPackage files.
All of those tools are documented by a ManPage, so if you have questions, you should consult them (eg. 'man apt'). If you're new, there are some commands that have proven most useful for everyday use. They are grouped generally as:
These are both console (ncurses) and GUI based. There are a number of alternatives, similar in some regards, different in others. For users of RPM-based Linux distros, analogs include RedCarpet and Up2Date.
aptitude may be invoked in full screen console mode (ncurses) or CLI mode, and is a friendly frontend to apt.
DSelect is an older frontend to apt. It is no longer recommended.
Synaptic is another GUI-based frontend.
Generally, the command line tools integrate a number of operations (package list management, package retrieval, package installation, package configuration) in a single command plus arguments. The primary command line tool is aptitude. apt-get fulfills a similar purpose and although it is no longer the recommended primary tool some still use it. Here are some typical invocations:
aptitude update (or apt-get update, see apt-get) to update apt's internal database of available packages
aptitude safe-upgrade (or apt-get -u upgrade) to bring all currently installed packages up to date
aptitude search jabber (or apt-cache search jabber) to find a program that gives you access to the jabber instant-messaging system
aptitude show gabber (or apt-cache show gabber) to display more info about the GNOME jabber client
aptitude install gabber (or apt-get install gabber) to install the package
aptitude remove gabber (or apt-get remove gabber) to remove it again
aptitude search '~i' to show installed packages
You can also use Wajig, for an unified and more logical command-line interface to all package management functions.
Largely dpkg and friends, these are commands that perform a single task. They are most directly comparable to Redhat's "rpm" command.
dpkg-reconfigure locales to reconfigure Locales
dpkg-reconfigure exim to reconfigure the exim mail-transfer agent. This command isn't currently part of dpkg; it's provided by debconf.
dpkg, (see DPkg) invoked with various command-line arguments. If you find a place to download debian-packages that is not accessible via apt, you can download the packages and install them directly. Note that this method will not automagically resolve dependencies between packages etc, therefore use apt or dselect if possible.
dpkg --listfiles textutils to list all the files provided by the textutils package. This only works for packages which are already installed. This can be useful to find out what form a package's documentation has been provided in.
dpkg -S /path/to/some/file to find out which package a file belongs to.
deborphan can be handy but is no longer required to recover space because apt now automatically un-installs unneeded packages that were installed only to satisfy a dependency of a package that was specifically requested to be installed but has since been removed. It gives you a list of library packages that no longer have higher-level packages depending on them.
Contents of a debian file
To see the contents of debian packages in the Debian repositories, whether installed or uninstalled, install the apt-file package and enter
$ apt-file update $ apt-file list foo
To get the contents of the file "abc.deb", you have to enter
$ dpkg-deb -c abc.deb
Reconfiguring of debconf
To reconfigure debconf, so that it informs you of most changes of the new packages, you have to enter (as Root):
# dpkg-reconfigure debconf
Chose "medium" here
Package Management with apt-get and dpkg
Package resource list for APT
The file /etc/apt/sources.list is the definition file of the sources for apt. For further information about this file type
$ man 5 sources.list
Retrieve new lists of packages:
To fetch the new lists of all the packages from sources.list enter:
# aptitude update
or the equivalent
# apt-get update
This command checks for new release-files on the given servers. Luckily the command is clever enough to check if the release-file has changed after the last update.
Upgrade of all the files:
To make an update of all the changed packages, enter the line
# aptitude safe-upgrade
If you want to do this from cron you should consider using the cron-apt package.
The older apt-get based method is:
# apt-get upgrade -u
The additional flag -u shows a list of upgraded packages as well. If you want to run the update in a cron-job, you should use the flags -dy. With this flags the new packages will be downloaded but not installed. You can install them later by writing apt-get update -u.
Distribution Upgrade of all the files:
Following the upgrade instructions found in the release notes is the best way to ensure that your system upgrades from one major Debian release to another (e.g. from lenny to squeeze) without breakage!
These instructions will tell you to do a dist-upgrade (instead of upgrade) at least once. You would have to type something like
# apt-get dist-upgrade -dy # apt-get dist-upgrade -u
at some point during the major release upgrade.
A dist-upgrade will also be required to keep up-to-date with the latest version in testing and unstable. A dist-upgrade may be very occasionally needed for you to obtain security upgrades in stable releases too in the case where packages change names.
Discover a package:
How can you discover which package to use without the GUI programs?
# apt-cache search sylpheed
Or use a web interface:
With the web search interface you can search the package contents for specific files:
Add a package:
How can you add a package to your system without the GUI programs? All you have to do is find out the name of this package and enter the command
# aptitude install sylpheed-claws
# apt-get install sylpheed-claws
to add the package sylpheed-claws.
Remove a package:
To get rid of the package foo which is no longer needed, enter the command
# aptitude remove foo
# apt-get remove foo
If the package is needed by other packages you will be prompted to remove this package and all packages which depend on it.
Forcing removal of a package:
While making a distribution upgrade it could happen that you have to remove a package first. But sometimes this is not possible with apt-get remove since the package has unmet dependencies or is not installed completely. You can remove the package foo by using the command
# dpkg --force-all --remove foo
Read the contents of a installed package:
Sometimes you want to know which files are in the package foo. To get this information enter the command
$ dpkg -L foo
Get the description of a package:
You don't know what the package foo is for? Just write
$ aptitude show foo
$ dpkg -p foo
Search the package of a file:
Have you ever wondered to which package a given file belongs? To get this information (e.g. for /usr/bin/apt-get), start the command
$ dpkg -S /usr/bin/apt-get
and it will tell you that this file is part of the package apt.