The Debian GNU/Linux FAQ
Chapter 7 - The Debian Package Management Tools
7.1 What programs does Debian provide for managing its packages?
7.1.1 dpkg
This is the main package management program. dpkg can be invoked
with many options. Some common uses are:
Find out all the options: dpkg --help.
Print out the control file (and other information) for a specified package:
dpkg --info foo_VVV-RRR.deb
Install a package (including unpacking and configuring) onto the file system of
the hard disk: dpkg --install foo_VVV-RRR.deb.
Unpack (but do not configure) a Debian archive into the file system of the hard
disk: dpkg --unpack foo_VVV-RRR.deb. Note that this operation
does not 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 What is a Debian preinst, postinst,
prerm, and postrm script?, Section 6.6) script associated with the package.
Configure a package that already has been unpacked: dpkg --configure
foo. Among other things, this action runs the postinst (see What is a Debian preinst, postinst,
prerm, and postrm script?, Section 6.6) script associated with the package.
It also updates the files listed in the conffiles for this
package. Notice that the 'configure' operation takes as its argument a package
name (e.g., foo), not the name of a Debian archive file (e.g.,
foo_VVV-RRR.deb).
Extract a single file named "blurf" (or a group of files named
"blurf*" from a Debian archive: dpkg --fsys-tarfile
foo_VVV-RRR.deb | tar -xf - blurf*
Remove a package (but not its configuration files): dpkg --remove
foo.
Remove a package (including its configuration files): dpkg --purge
foo.
List the installation status of packages containing the string (or regular
expression) "foo*": dpkg --list 'foo*'.
7.1.2 dselect
This program is a menu-driven interface to the Debian package management
system. It is particularly useful for first-time installations and large-scale
upgrades.
dselect can:
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;
warn the user about inconsistencies or incompatibilities in their selections;
determine the order in which the packages must be installed;
automatically perform the installation or removal; and
guide the user through whatever configuration process are required for each
package.
dselect 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
<enter> key to select the highlighted action.
What the user sees next depends on the action he selected. If he selects any
option but Access or Select, then
dselect will simply proceed to execute the specified action: e.g.,
if the user selected the action Remove, then dselect would proceed
to remove all of the files selected for removal when the user last chose the
Select action.
Both the Access menu item and the Select 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.
Extensive on-line help is available, use the '?' key to get to a help screen
at any time.
The order in which the actions are presented in the first dselect
menu represents the order in which a user would normally choose
dselect 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).
Begin by choosing an Access Method. 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
dselect exits, so if it does not change, then this option need not
be invoked again.
Then Update the list of available packages. To do this,
dselect 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, dselect will offer
to make it for you.)
Select 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).
The top part of the screen is a relatively narrow window into the list of
Debian's 8250 packages; the bottom part of the screen contains description of
the package or group of packages which are highlighted above.
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:
to be installed:
This is accomplished by pressing the `+' key.
to be deleted:
Packages can be deleted two ways:
removed: this removes most of the files associated with the package, but
preserves the files listed as configuration files (see What is a Debian conffile?, Section
6.5) and package configuration information. This is done by pressing the
`-' key.
purged: this removes every file that is part of the package. This is
done by pressing the `_' key.
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.
to be put "on hold"
This is done by pressing `=', and it effectively tells dselect 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 Access Method, and
acquired when you used Update).
Just like you can put a package on hold, you can reverse such setting by
pressing `:'. That tells dselect that the package(s) may be
upgraded if a newer version is available. This is the default setting.
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.
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.
If you select a package for installation or removal, e.g.,
foo.deb, and that package depends on (or recommends) another
package, e.g., blurf.deb, then dselect 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.
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 dselect.
7.1.3 dpkg-deb
This program manipulates Debian archive(.deb) files. Some common
uses are:
Find out all the options: dpkg-deb --help.
Determine what files are contained in a Debian archive file: dpkg-deb
--contents foo_VVV-RRR.deb)
Extract the files contained in a named Debian archive into a user specified
directory: dpkg-deb --extract foo_VVV-RRR.deb tmp extracts each of
the files in foo_VVV-RRR.deb into the directory tmp/.
This is convenient for examining the contents of a package in a localized
directory, without installing the package into the root file system.
Note that any packages that were merely unpacked using dpkg-deb
--extract will be incorrectly installed, you should use dpkg
--install instead.
More information is given in the manual page dpkg-deb(1).
7.1.4 apt-get
apt-get provides a simple way to install packages from the command
line. Unlike dpkg, apt-get does not understand .deb
files, it works with the packages proper name and can only install .deb
archives from a source specified in /etc/apt/sources.list.
For more information, install apt package and read
apt-get(8), sources.list(5) and
/usr/share/doc/apt/guide.html/index.html.
7.1.5 dpkg-split
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 dpkg package), since it calls the program
dpkg-deb to parse the debian package file into its component
records.
For example, to split a big .deb file into N parts,
Execute the command dpkg-split --split foo.deb. This will produce
N files each of approximately 460 KBytes long in the current directory.
Copy those N files to floppy disks.
Copy the contents of the floppy disks onto the hard disk of your choice on the
other machine.
Join those part-files together using dpkg-split --join
"foo*".
7.2 Debian claims to be able to update a running program; how is this accomplished?
The kernel (filesystem) in Debian GNU/Linux systems supports replacing files
even while they're being used.
We also provide a program called start-stop-daemon 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.
7.3 How can I tell what packages are already installed on a Debian system?
To learn the status of all the packages installed on a Debian system, execute
the command
dpkg --list
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
installed, and a brief description.
To learn the status of packages whose names match the string any pattern
beginning with "foo" by executing the command:
dpkg --list 'foo*'
To get a more verbose report for a particular package, execute the command:
dpkg --status packagename
7.4 How can I find out what package produced a particular file?
To identify the package that produced the file named foo execute
either:
dpkg --search filename
This searches for filename in installed packages. (This is
(currently) equivalent to searching all of the files having the file extension
of .list in the directory /var/lib/dpkg/info/, and
adjusting the output to print the names of all the packages containing it, and
diversions.)
zgrep foo Contents-ARCH.gz
This searches for files which contain the substring foo in their
full path names. The files Contents-ARCH.gz (where ARCH
represents the wanted architecture) reside in the major package directories
(main, non-free, contrib) at a Debian FTP site. A Contents file
refers only to the packages in the subdirectory tree where it resides.
Therefore, a user might have to search more than one Contents
files to find the package containing the file foo.
This method has the advantage over dpkg --search in that it will
find files in packages that are not currently installed on your system.