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<hr>
<h1>
The Debian GNU/Linux FAQ
<br>Chapter 7 - The Debian package management tools
</h1>
<hr>
<h2><a name="s-pkgprogs"></a>7.1 What programs does Debian provide for managing its packages?</h2>
<p>
There are multiple tools that are used to manage Debian packages, from graphic
or text-based interfaces to the low level tools used to install packages. All
the available tools rely on the lower level tools to properly work and are
presented here in decreasing complexity level.
</p>
<p>
It is important to understand that the higher level package management tools
such as <code>aptitude</code> or <code>dselect</code> rely on <code>apt</code>
which, itself, relies on <code>dpkg</code> to manage the packages in the
system.
</p>
<p>
See the <code><a href="http://www.debian.org/doc/manuals/apt-howto/">APT
HOWTO</a></code> for more information about the Debian package management
utilities. This document is available in various languages and formats, see
<code><a href="http://www.debian.org/doc/user-manuals#apt-howto">the APT HOWTO
entry on the DDP Users' Manuals overview</a></code>.
</p>
<hr>
<h3><a name="s-dpkg"></a>7.1.1 dpkg</h3>
<p>
This is the main package management program. <code>dpkg</code> can be invoked
with many options. Some common uses are:
</p>
<ul>
<li>
<p>
Find out all the options: <samp>dpkg --help</samp>.
</p>
</li>
</ul>
<ul>
<li>
<p>
Print out the control file (and other information) for a specified package:
<samp>dpkg --info foo_VVV-RRR.deb</samp>
</p>
</li>
</ul>
<ul>
<li>
<p>
Install a package (including unpacking and configuring) onto the file system of
the hard disk: <samp>dpkg --install foo_VVV-RRR.deb</samp>.
</p>
</li>
</ul>
<ul>
<li>
<p>
Unpack (but do not configure) a Debian archive into the file system of the hard
disk: <samp>dpkg --unpack foo_VVV-RRR.deb</samp>. Note that this operation
does <em>not</em> necessarily leave the package in a usable state; some files
may need further customization to run properly. This command removes any
already-installed version of the program and runs the preinst (see <a
href="ch-pkg_basics.en.html#s-maintscripts">What is a Debian preinst, postinst,
prerm, and postrm script?, Section 6.6</a>) script associated with the package.
</p>
</li>
</ul>
<ul>
<li>
<p>
Configure a package that already has been unpacked: <samp>dpkg --configure
foo</samp>. Among other things, this action runs the postinst (see <a
href="ch-pkg_basics.en.html#s-maintscripts">What is a Debian preinst, postinst,
prerm, and postrm script?, Section 6.6</a>) script associated with the package.
It also updates the files listed in the <samp>conffiles</samp> for this
package. Notice that the 'configure' operation takes as its argument a package
name (e.g., foo), <em>not</em> the name of a Debian archive file (e.g.,
foo_VVV-RRR.deb).
</p>
</li>
</ul>
<ul>
<li>
<p>
Extract a single file named "blurf" (or a group of files named
"blurf*" from a Debian archive: <samp>dpkg --fsys-tarfile
foo_VVV-RRR.deb | tar -xf - blurf*</samp>
</p>
</li>
</ul>
<ul>
<li>
<p>
Remove a package (but not its configuration files): <samp>dpkg --remove
foo</samp>.
</p>
</li>
</ul>
<ul>
<li>
<p>
Remove a package (including its configuration files): <samp>dpkg --purge
foo</samp>.
</p>
</li>
</ul>
<ul>
<li>
<p>
List the installation status of packages containing the string (or regular
expression) "foo*": <samp>dpkg --list 'foo*'</samp>.
</p>
</li>
</ul>
<hr>
<h3><a name="s-apt-get"></a>7.1.2 APT</h3>
<p>
APT is the <em>Advanced Package Tool</em> and provides the <code>apt-get</code>
program. <code>apt-get</code> provides a simple way to retrieve and install
packages from multiple sources using the command line. Unlike
<code>dpkg</code>, <code>apt-get</code> does not understand .deb files, it
works with the packages proper name and can only install .deb archives from a
source specified in <code>/etc/apt/sources.list</code>. <code>apt-get</code>
will call <code>dpkg</code> directly after downloading the .deb archives[<a
href="footnotes.en.html#f4" name="fr4">4</a>] from the configured sources.
</p>
<p>
Some common ways to use <code>apt-get</code> are:
</p>
<ul>
<li>
<p>
To update the list of package known by your system, you can run:
</p>
<pre>
apt-get update
</pre>
<p>
(you should execute this regularly to update your package lists)
</p>
</li>
</ul>
<ul>
<li>
<p>
To upgrade all the packages on your system, run:
</p>
<pre>
apt-get upgrade
</pre>
</li>
</ul>
<ul>
<li>
<p>
To install the <var>foo</var> package and all its dependencies, run:
</p>
<pre>
apt-get install foo
</pre>
</li>
</ul>
<ul>
<li>
<p>
To remove the foo package from your system, run:
</p>
<pre>
apt-get remove foo
</pre>
</li>
</ul>
<ul>
<li>
<p>
To remove the foo package and its configuration files from your system, run:
</p>
<pre>
apt-get --purge remove foo
</pre>
</li>
</ul>
<ul>
<li>
<p>
To upgrade all the packages on your system to a new Debian GNU/Linux release,
run:
</p>
<pre>
apt-get dist-upgrade
</pre>
</li>
</ul>
<p>
Note that you must be logged in as root to perform any commands that modify the
system packages.
</p>
<p>
The apt tool suite also includes the <code>apt-cache</code> tool to query the
package lists. You can use it to find packages providing specific
functionality through simple text or regular expression queries and through
queries of dependencies in the package management system. Some common ways to
use <code>apt-cache</code> are:
</p>
<ul>
<li>
<p>
To find packages whose description contain <var>word</var>:
</p>
<pre>
apt-cache search <var>word</var>
</pre>
</li>
</ul>
<ul>
<li>
<p>
To print the detailed information of a package:
</p>
<pre>
apt-cache show <var>package</var>
</pre>
</li>
</ul>
<ul>
<li>
<p>
To print the packages a given package depends on:
</p>
<pre>
apt-cache depends <var>package</var>
</pre>
</li>
</ul>
<ul>
<li>
<p>
To print detailed information of the versions available for a package and the
packages that reverse-depends on it:
</p>
<pre>
apt-cache showpkg <var>package</var>
</pre>
</li>
</ul>
<p>
For more information, install the <code>apt</code> package and read
<code>apt-get(8)</code>, <code>sources.list(5)</code> and install the
<code>apt-doc</code> package and read
<code>/usr/share/doc/apt-doc/guide.html/index.html</code>.
</p>
<hr>
<h3><a name="s-aptitude"></a>7.1.3 aptitude</h3>
<p>
<code>aptitude</code> is a package manager for Debian GNU/Linux systems that
provides a frontend to the apt package management infrastructure.
<code>aptitude</code> is a text-based interface using the curses library, it
can be used to perform management tasks in a fast and easy way.
</p>
<p>
<code>aptitude</code> provides the functionality of <code>dselect</code> and
<code>apt-get</code>, as well as many additional features not found in either
program:
</p>
<ul>
<li>
<p>
<code>aptitude</code> offers access to all versions of a package.
</p>
</li>
</ul>
<ul>
<li>
<p>
<code>aptitude</code> logs all its actions in <code>/var/log/aptitude</code>.
</p>
</li>
</ul>
<ul>
<li>
<p>
<code>aptitude</code> makes it easy to keep track of obsolete software by
listing it under "Obsolete and Locally Created Packages".
</p>
</li>
</ul>
<ul>
<li>
<p>
<code>aptitude</code> includes a fairly powerful system for searching
particular packages and limiting the package display. Users familiar with
<code>mutt</code> will pick up quickly, as <code>mutt</code> was the
inspiration for the expression syntax.
</p>
</li>
</ul>
<ul>
<li>
<p>
<code>aptitude</code> tracks which packages have been installed due to
dependencies and removes them automatically when the packages that needed them
are removed from the system.
</p>
</li>
</ul>
<ul>
<li>
<p>
<code>aptitude</code> can automatically install <em>Recommended:</em>
packages[<a href="footnotes.en.html#f5" name="fr5">5</a>].
</p>
</li>
</ul>
<ul>
<li>
<p>
<code>aptitude</code> in full screen mode has <code>su</code> functionality
embedded and can be run by a normal user. It will call <code>su</code> (and
ask for the root password, if any) when you really need administrative
privileges
</p>
</li>
</ul>
<p>
You can use <code>aptitude</code> through a visual interface (simply run
<samp>aptitude</samp>) or directly from the command line. The command line
syntax used is very similar to the one used in <code>apt-get</code>. For
example, to install the <var>foo</var> package, you can run <samp>aptitude
install <var>foo</var></samp>.
</p>
<p>
Note that <code>aptitude</code> is the recommended program by Debian to install
a package and/or to upgrade your system.
</p>
<p>
For more informations, read the manual page <code>aptitude(8)</code> and
install the <code>aptitude-doc-en</code> package.
</p>
<hr>
<h3><a name="s-dselect"></a>7.1.4 dselect</h3>
<p>
This program is a menu-driven interface to the Debian package management
system. It is particularly useful for first-time installations. Some users
might feel more comfortable using <code>aptitude</code> which is also
recommended over <code>dselect</code> for large-scale upgrades. For more
information on <code>aptitude</code> please see <a href="#s-aptitude">aptitude,
Section 7.1.3</a>.
</p>
<p>
<code>dselect</code> can:
</p>
<ul>
<li>
<p>
guide the user as he/she chooses among packages to install or remove, ensuring
that no packages are installed that conflict with one another, and that all
packages required to make each package work properly are installed;
</p>
</li>
</ul>
<ul>
<li>
<p>
warn the user about inconsistencies or incompatibilities in their selections;
</p>
</li>
</ul>
<ul>
<li>
<p>
determine the order in which the packages must be installed;
</p>
</li>
</ul>
<ul>
<li>
<p>
automatically perform the installation or removal; and
</p>
</li>
</ul>
<ul>
<li>
<p>
guide the user through whatever configuration process are required for each
package.
</p>
</li>
</ul>
<p>
<code>dselect</code> begins by presenting the user with a menu of 7 items, each
of which is a specific action. The user can select one of the actions by using
the arrow keys to move the highlighter bar, then pressing the
<em><enter></em> key to select the highlighted action.
</p>
<p>
What the user sees next depends on the action he selected. If he selects any
option but <samp>Access</samp> or <samp>Select</samp>, then
<code>dselect</code> will simply proceed to execute the specified action: e.g.,
if the user selected the action <samp>Remove</samp>, then dselect would proceed
to remove all of the files selected for removal when the user last chose the
<samp>Select</samp> action.
</p>
<p>
Both the <samp>Access</samp> menu item and the <samp>Select</samp> menu item
lead to additional menus. In both cases, the menus are presented as split
screens; the top screen gives a scrollable list of choices, while the bottom
screen gives a brief explanation ("info") for each choice.
</p>
<p>
Extensive on-line help is available, use the '?' key to get to a help screen
at any time.
</p>
<p>
The order in which the actions are presented in the first <code>dselect</code>
menu represents the order in which a user would normally choose
<code>dselect</code> to install packages. However, a user can pick any of the
main menu choices as often as needed (including not at all, depending on what
one wants to do).
</p>
<ul>
<li>
<p>
Begin by choosing an <strong>Access Method</strong>. This is the method by
which the user plans on accessing Debian packages; e.g., some users have Debian
packages available on CD-ROM, while others plan to fetch them using anonymous
FTP. The selected "Access Method" is stored after
<code>dselect</code> exits, so if it does not change, then this option need not
be invoked again.
</p>
</li>
</ul>
<ul>
<li>
<p>
Then <strong>Update</strong> the list of available packages. To do this,
<code>dselect</code> reads the file "Packages.gz" which should be
included in the top level of the directory where the Debian packages to be
installed are stored. (But if it is not there, <code>dselect</code> will offer
to make it for you.)
</p>
</li>
</ul>
<ul>
<li>
<p>
<strong>Select</strong> specific packages for installation on his system.
After choosing this menu item, the user is first presented with a full screen
of help (unless the `--expert' command line option was used). Once the user
exits the Help screen, he sees the split-screen menu for choosing packages to
install (or remove).
</p>
<p>
The top part of the screen is a relatively narrow window into the list of
Debian's 18347 packages; the bottom part of the screen contains description of
the package or group of packages which are highlighted above.
</p>
<p>
One can specify which packages should be operated on by highlighting a package
name or the label for a group of packages. After that, you can select
packages:
</p>
<dl>
<dt>to be installed:</dt>
<dd>
<p>
This is accomplished by pressing the `+' key.
</p>
</dd>
</dl>
<dl>
<dt>to be deleted:</dt>
<dd>
<p>
Packages can be deleted two ways:
</p>
<ul>
<li>
<p>
removed: this removes most of the files associated with the package, but
preserves the files listed as configuration files (see <a
href="ch-pkg_basics.en.html#s-conffile">What is a Debian conffile?, Section
6.5</a>) and package configuration information. This is done by pressing the
`-' key.
</p>
</li>
</ul>
<ul>
<li>
<p>
purged: this removes <em>every</em> file that is part of the package. This is
done by pressing the `_' key.
</p>
</li>
</ul>
<p>
Note that it's not possible to remove "All Packages". If you try
that, your system will instead be reduced to the initial installed base
packages.
</p>
</dd>
</dl>
<dl>
<dt>to be put "on hold"</dt>
<dd>
<p>
This is done by pressing `=', and it effectively tells <code>dselect</code> not
to upgrade a package even if the version currently installed on your system is
not as recent as the version that is available in the Debian repository you are
using (this was specified when you set the <strong>Access Method</strong>, and
acquired when you used <strong>Update</strong>).
</p>
<p>
Just like you can put a package on hold, you can reverse such setting by
pressing `:'. That tells <code>dselect</code> that the package(s) may be
upgraded if a newer version is available. This is the default setting.
</p>
</dd>
</dl>
<p>
You can select a different order in which the packages are presented, by using
the `o' key to cycle between various options for sorting the packages. The
default order is to present packages by Priority; within each priority,
packages are presented in order of the directory (a.k.a. section) of the
archive in which they are stored. Given this sort order, some packages in
section A (say) may be presented first, followed by some packages in section B,
followed by more packages (of lower priority) in section A.
</p>
<p>
You can also expand meanings of the labels at the top of the screen, by using
the `v' (verbose) key. This action pushes much of the text that formerly fit
onto the display off to the right. To see it, press the right arrow; to scroll
back to the left, press the left arrow.
</p>
<p>
If you select a package for installation or removal, e.g.,
<code>foo.deb</code>, and that package depends on (or recommends) another
package, e.g., <code>blurf.deb</code>, then <code>dselect</code> will place the
you in a sub-screen of the main selection screen. There you can choose among
the related packages, accepting the suggested actions (to install or not), or
rejecting them. To do the latter, press Shift-D; to return to the former,
press Shift-U. In any case, you can save your selections and return to the
main selection screen by pressing Shift-Q.
</p>
</li>
</ul>
<ul>
<li>
<p>
Users returning to the main menu can then select the "Install" menu
item to unpack and configure the selected packages. Alternatively, users
wishing to remove files can choose the "Remove" menu item. At any
point, users can choose "Quit" to exit dselect; users' selections are
preserved by <code>dselect</code>.
</p>
</li>
</ul>
<hr>
<h3><a name="s-dpkg-extra"></a>7.1.5 Other package management tools</h3>
<hr>
<h4><a name="s-dpkg-deb"></a>7.1.5.1 dpkg-deb</h4>
<p>
This program manipulates Debian archive(<samp>.deb</samp>) files. Some common
uses are:
</p>
<ul>
<li>
<p>
Find out all the options: <samp>dpkg-deb --help</samp>.
</p>
</li>
</ul>
<ul>
<li>
<p>
Determine what files are contained in a Debian archive file: <samp>dpkg-deb
--contents foo_VVV-RRR.deb</samp>)
</p>
</li>
</ul>
<ul>
<li>
<p>
Extract the files contained in a named Debian archive into a user specified
directory: <samp>dpkg-deb --extract foo_VVV-RRR.deb tmp</samp> extracts each of
the files in <samp>foo_VVV-RRR.deb</samp> into the directory <samp>tmp/</samp>.
This is convenient for examining the contents of a package in a localized
directory, without installing the package into the root file system.
</p>
</li>
</ul>
<p>
Note that any packages that were merely unpacked using <samp>dpkg-deb
--extract</samp> will be incorrectly installed, you should use <samp>dpkg
--install</samp> instead.
</p>
<p>
More information is given in the manual page <code>dpkg-deb(1)</code>.
</p>
<hr>
<h4><a name="s-dpkg-split"></a>7.1.5.2 dpkg-split</h4>
<p>
This program splits large package into smaller files (e.g., for writing onto a
set of floppy disks), and can also be used to merge a set of split files back
into a single file. It can only be used on a Debian system (i.e. a system
containing the <code>dpkg</code> package), since it calls the program
<samp>dpkg-deb</samp> to parse the debian package file into its component
records.
</p>
<p>
For example, to split a big .deb file into N parts,
</p>
<ul>
<li>
<p>
Execute the command <samp>dpkg-split --split foo.deb</samp>. This will produce
N files each of approximately 460 KBytes long in the current directory.
</p>
</li>
</ul>
<ul>
<li>
<p>
Copy those N files to floppy disks.
</p>
</li>
</ul>
<ul>
<li>
<p>
Copy the contents of the floppy disks onto the hard disk of your choice on the
other machine.
</p>
</li>
</ul>
<ul>
<li>
<p>
Join those part-files together using <samp>dpkg-split --join
"foo*"</samp>.
</p>
</li>
</ul>
<hr>
<h2><a name="s-updaterunning"></a>7.2 Debian claims to be able to update a running program; how is this accomplished?</h2>
<p>
The kernel (file system) in Debian GNU/Linux systems supports replacing files
even while they're being used.
</p>
<p>
We also provide a program called <code>start-stop-daemon</code> which is used
to start daemons at boot time or to stop daemons when the kernel runlevel is
changed (e.g., from multi-user to single-user or to halt). The same program is
used by installation scripts when a new package containing a daemon is
installed, to stop running daemons, and restart them as necessary.
</p>
<hr>
<h2><a name="s-whatpackages"></a>7.3 How can I tell what packages are already installed on a Debian system?</h2>
<p>
To learn the status of all the packages installed on a Debian system, execute
the command
</p>
<pre>
dpkg --list
</pre>
<p>
This prints out a one-line summary for each package, giving a 2-letter status
symbol (explained in the header), the package name, the version which is
<em>installed</em>, and a brief description.
</p>
<p>
To learn the status of packages whose names match the string any pattern
beginning with "foo" by executing the command:
</p>
<pre>
dpkg --list 'foo*'
</pre>
<p>
To get a more verbose report for a particular package, execute the command:
</p>
<pre>
dpkg --status packagename
</pre>
<hr>
<h2><a name="s-filesearch"></a>7.4 How can I find out what package produced a particular file?</h2>
<p>
To identify the package that produced the file named <samp>foo</samp> execute
either:
</p>
<ul>
<li>
<p>
<samp>dpkg --search filename</samp>
</p>
<p>
This searches for <samp>filename</samp> in installed packages. (This is
(currently) equivalent to searching all of the files having the file extension
of <samp>.list</samp> in the directory <samp>/var/lib/dpkg/info/</samp>, and
adjusting the output to print the names of all the packages containing it, and
diversions.)
</p>
<p>
A faster alternative to this is the <code>dlocate</code> tool.
</p>
</li>
</ul>
<ul>
<li>
<p>
<samp>zgrep foo Contents-ARCH.gz</samp>
</p>
<p>
This searches for files which contain the substring <samp>foo</samp> in their
full path names. The files <samp>Contents-ARCH.gz</samp> (where ARCH
represents the wanted architecture) reside in the major package directories
(main, non-free, contrib) at a Debian FTP site (i.e. under
<samp>/debian/dists/etch</samp>). A <samp>Contents</samp> file refers only to
the packages in the subdirectory tree where it resides. Therefore, a user
might have to search more than one <samp>Contents</samp> files to find the
package containing the file <samp>foo</samp>.
</p>
<p>
This method has the advantage over <samp>dpkg --search</samp> in that it will
find files in packages that are not currently installed on your system.
</p>
</li>
</ul>
<ul>
<li>
<p>
<samp>apt-file search <var>foo</var></samp>
</p>
<p>
Similar to the above, it searches files which contain the substring or regular
expression <samp>foo</samp> in their full path names. The advantage over the
sample above is that there is no need to retrieve the
<samp>Contents-ARCH.gz</samp> files as it will do this automatically for all
the sources defined in <code>/etc/apt/sources.list</code> when you run (as
root) <samp>apt-file update</samp>.
</p>
</li>
</ul>
<hr>
<h2><a name="s-datapackages"></a>7.5 Why doesn't get `foo-data' removed when I uninstall `foo'? How do I make sure old unused library-packages get purged?</h2>
<p>
Some packages that are split in program (`foo') and data (`foo-data'). This is
true for many games, multimedia applications and dictionaries in Debian and has
been introduced since some users might want to access the raw data without
installing the program or because the program can be run without the data
itself, making it optional.
</p>
<p>
Similar situations occur when dealing with libraries: generally these get
installed since packages containing applications depend on them. When the
application-package is purged, the library-package might stay on the system.
Or: when the application-package no longer depends upon e.g. libdb4.2, but
upon libdb4.3, the libdb4.2 package might stay when the application-package is
upgraded.
</p>
<p>
In these cases, `foo-data' doesn't depend on `foo', so when you remove the
`foo' package it will not get automatically removed by most package management
tools. The same holds true for the library packages. This is necessary to
avoid circular dependencies. If you use <code>aptitude</code> (see <a
href="#s-aptitude">aptitude, Section 7.1.3</a>) as your package management tool
it will, however, track automatically installed packages and remove them when
no packages remain that need them in your system.
</p>
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The Debian GNU/Linux FAQ
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version 3.1.5, 17 January 2007<br>
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