![Close [x]](http://dw1.s81c.com/i/c.gif){kind=small}
In this article, learn to use the Debian package management tools to manage the packages on your Linux system. Learn to:
- Install, reinstall, upgrade, and remove Debian binary packages
- Find packages containing specific files or libraries, even if the package is not installed
- Obtain package information like version, content, dependencies, package integrity, and installation status, even if the package is not installed
This article helps you prepare for Objective 102.4 in Topic 102 of the Linux Professional Institute's Junior Level Administration (LPIC-1) exam 101. The objective has a weight of 3.
To get the most from the articles in this series, you should have a basic knowledge of Linux and a working Linux system on which you can practice the commands covered in this article. Sometimes different versions of a program will format output differently, so your results may not always look exactly like the listings and figures shown here. In particular, much of the output we show is highly dependent on the packages that are already installed on our systems. Your own output may be quite different, although you should be able to recognize the important commonalities.
Introducing package management
In the past, many Linux programs were distributed as source code, which a user would build into the required program or set of programs, along with the required man pages, configuration files, and so on. Nowadays, most Linux distributors use prebuilt programs or sets of programs called packages, which ship ready for installation on that distribution. In this article, you will learn about package management tools that help you install, update, and remove packages. This article focuses on Advanced Packaging Tool, or APT, the package management system used by Debian and distributions derived from Debian, such as Ubuntu. Another article in this series, "Learn Linux 101: RPM and YUM package management," covers the Red Hat package management tools.
From a user perspective, the basic package management function is provided by commands. As Linux developers have striven to make Linux easier to use, the basic tools have been supplemented by other tools, including GUI tools, which hide some of the complexities of the basic tools from the end user. In this article and in the article on RPM and YUM package management, we focus on the basic tools, although we mention some of the other tools so you can pursue them further.
APT, RPM, and YUM (the latter two are package management tools for Red Hat systems) have many similarities. All can install and remove packages. Information about installed packages is kept in a database. All have basic command-line functionality, while additional tools can provide more user-friendly interfaces. All can retrieve packages from the Internet.
When you install a Linux system, you typically install a large selection of packages. The set may be customized to the intended use of the system, such as a server, desktop, or developer workstation. And at some time, you will probably need to install new packages for added functionality, update the packages you have, or even remove packages that you no longer need or that have been made obsolete by newer packages. Let's look at how you do these tasks, and at some of the related challenges such as finding which package might contain a particular command.
Suppose you want to learn Lisp, and a colleague tells you to use the
gcl command. You might try
gcl --help, or you might try
which gcl, or
type gcl. But if your system can't
find gcl, you might see output similar to that
shown in Listing 1.
Listing 1. Missing gcl command
ian@pinguino:~$ gcl --help
-bash: gcl: command not found
ian@pinguino:~$ gcl --help
The program 'gcl' is currently not installed. You can install it by typing:
sudo apt-get install gcl
gcl: command not found
ian@pinguino:~$ which gcl
ian@pinguino:~$ type gcl
-bash: type: gcl: not found |
If you did not get the helpful suggestion from the second form of output in
Listing 1, you might check back with your colleague to find out which
package to install. Otherwise, you might just guess that the
gcl command is in the gcl package. This is
often a good guess, but not always the right one. We'll see later how to
find the right package. In this case, you need the gcl package, and you
install it using the apt-get command with the
install option as shown in Listing 2. Note that
apt-get will determine which extra packages you
need to satisfy dependencies and will then give you a list of all the packages
that will be installed. At that point, you are prompted to continue. In our
example, we respond y to install gcl and the additional required
package, libreadline5.
Listing 2. Installing gcl using apt-get
ian@pinguino:~$ sudo apt-get install gcl [sudo] password for ian: Reading package lists... Done Building dependency tree Reading state information... Done The following packages were automatically installed and are no longer required: linux-headers-2.6.31-14 linux-headers-2.6.31-14-generic Use 'apt-get autoremove' to remove them. The following extra packages will be installed: libreadline5 Suggested packages: gcl-doc The following NEW packages will be installed: gcl libreadline5 0 upgraded, 2 newly installed, 0 to remove and 30 not upgraded. Need to get 47.1MB of archives. After this operation, 157MB of additional disk space will be used. Do you want to continue [Y/n]? y Get:1 http://us.archive.ubuntu.com karmic/main libreadline5 5.2-6 [140kB] Get:2 http://us.archive.ubuntu.com karmic/universe gcl 2.6.7-45ubuntu1 [47.0MB] Fetched 47.1MB in 1min 33s (502kB/s) Preconfiguring packages ... Selecting previously deselected package libreadline5. (Reading database ... 142156 files and directories currently installed.) Unpacking libreadline5 (from .../libreadline5_5.2-6_i386.deb) ... Selecting previously deselected package gcl. Unpacking gcl (from .../gcl_2.6.7-45ubuntu1_i386.deb) ... Processing triggers for man-db ... Setting up libreadline5 (5.2-6) ... Setting up gcl (2.6.7-45ubuntu1) ... install/gcl: Handling install for emacsen flavor emacs22 Loading 00debian-vars... No /etc/mailname. Reverting to default... Loading /etc/emacs/site-start.d/50dictionaries-common.el (source)... Loading debian-ispell... Loading /var/cache/dictionaries-common/emacsen-ispell-default.el (source)... Loading /var/cache/dictionaries-common/emacsen-ispell-dicts.el (source)... Loading /etc/emacs/site-start.d/50gcl.el (source)... Wrote /usr/share/emacs22/site-lisp/gcl/add-default.elc Wrote /usr/share/emacs22/site-lisp/gcl/ansi-doc.elc Wrote /usr/share/emacs22/site-lisp/gcl/dbl.elc Wrote /usr/share/emacs22/site-lisp/gcl/doc-to-texi.elc Wrote /usr/share/emacs22/site-lisp/gcl/gcl.elc Wrote /usr/share/emacs22/site-lisp/gcl/man1-to-texi.elc Wrote /usr/share/emacs22/site-lisp/gcl/smart-complete.elc Wrote /usr/share/emacs22/site-lisp/gcl/sshell.elc install/gcl: Handling install for emacsen flavor emacs23 Loading 00debian-vars... No /etc/mailname. Reverting to default... Loading /etc/emacs/site-start.d/50dictionaries-common.el (source)... Loading debian-ispell... Loading /var/cache/dictionaries-common/emacsen-ispell-default.el (source)... Loading /var/cache/dictionaries-common/emacsen-ispell-dicts.el (source)... Loading /etc/emacs/site-start.d/50gcl.el (source)... Wrote /usr/share/emacs23/site-lisp/gcl/add-default.elc Wrote /usr/share/emacs23/site-lisp/gcl/ansi-doc.elc Wrote /usr/share/emacs23/site-lisp/gcl/dbl.elc Wrote /usr/share/emacs23/site-lisp/gcl/doc-to-texi.elc Wrote /usr/share/emacs23/site-lisp/gcl/gcl.elc Wrote /usr/share/emacs23/site-lisp/gcl/man1-to-texi.elc Wrote /usr/share/emacs23/site-lisp/gcl/smart-complete.elc Wrote /usr/share/emacs23/site-lisp/gcl/sshell.elc Processing triggers for libc-bin ... ldconfig deferred processing now taking place |
From the output in Listing 2, you see that apt-get
has read a package list from somewhere
(more on that shortly), built a dependency tree, and determined that
libreadline5 is a required prerequisite that is not currently installed.
You will also notice the suggestion to install the separate package for
the documentation, gcl-doc. After some additional summary information,
including space usage, you are prompted to continue, and gcl is installed
along with the prerequisite package. Debian packages usually have an
extension of .deb, and you see that the packages are downloaded and
unpacked as shown in the line:
Unpacking gcl (from .../gcl_2.6.7-45ubuntu1_i386.deb)
...
Suppose that, instead of installing a package, you simply want to find out
whether the package depends on other packages. You can use the
-s (for simulate) option on apt-get.
There are several other options with equivalent function, such as
--just-print and
\--dry-run. Check the man pages for full
details. Listing 3 shows what happens for a simulation of installing the
gcl-doc package.
Listing 3. Simulated or dry-run install of gcl-doc
ian@pinguino:~$ sudo apt-get install -s gcl-doc Reading package lists... Done Building dependency tree Reading state information... Done The following packages were automatically installed and are no longer required: linux-headers-2.6.31-14 linux-headers-2.6.31-14-generic Use 'apt-get autoremove' to remove them. The following NEW packages will be installed: gcl-doc 0 upgraded, 1 newly installed, 0 to remove and 30 not upgraded. Inst gcl-doc (2.6.7-45ubuntu1 Ubuntu:9.10/karmic) Conf gcl-doc (2.6.7-45ubuntu1 Ubuntu:9.10/karmic) |
Not surprisingly, the documentation does not have any prerequisite packages.
In the previous section, you learned how to install a Debian package. But
where do the packages come from? How does
apt-get know where to download packages from?
We mentioned that apt-get read a package list from somewhere. The starting
point for that somewhere is /etc/apt/sources.list. The list tells
apt-get where to look for packages, including
from a
CD-ROM, from your local file system, or over a network using http or ftp. You
can add additional sources in the /etc/apt/sources.list.d directory.
Listing 4 shows the first few lines of /etc/apt/sources.list on my system. Note that the distribution CD on the first line is commented out (# in position 1). If you need to install a lot of new packages that may not have been heavily updated, it may be worthwhile to uncomment this and install from your distribution CD or DVD. If you have a broadband network connection or need a lot of updates, it may be more efficient to just download the additional packages at the latest level from the network sources that follow in /etc/apt/sources.list.
Listing 4. /etc/apt/sources.list
ian@pinguino:~$ cat /etc/apt/sources.list #deb cdrom:[Ubuntu 9.10 _Karmic Koala_ - Release i386 (20091028.5)]/ karmic main restrict ed # See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to # newer versions of the distribution. deb http://us.archive.ubuntu.com/ubuntu/ karmic main restricted deb-src http://us.archive.ubuntu.com/ubuntu/ karmic main restricted ## Major bug fix updates produced after the final release of the ## distribution. deb http://us.archive.ubuntu.com/ubuntu/ karmic-updates main restricted deb-src http://us.archive.ubuntu.com/ubuntu/ karmic-updates main restricted ## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu ## team. Also, please note that software in universe WILL NOT receive any ## review or updates from the Ubuntu security team. deb http://us.archive.ubuntu.com/ubuntu/ karmic universe deb-src http://us.archive.ubuntu.com/ubuntu/ karmic universe deb http://us.archive.ubuntu.com/ubuntu/ karmic-updates universe deb-src http://us.archive.ubuntu.com/ubuntu/ karmic-updates universe |
Apt-get and similar tools use a local database to
determine what packages are installed. They can check installed levels
against available levels. To do this, information on available levels is
retrieved from the sources listed in /etc/apt/sources.list and stored on
your local system. You use the command
apt-get update to synchronize the
information in your local database with the sources specified in
/etc/apt/sources.list. You should do this before installing or updating
any package, and always after modifying /etc/apt/sources.list or adding
files to /etc/apt/sources.list.d.
If you want to remove a package, you can use the
remove option of
apt-get. A simulated run is shown in Listing
5.
Listing 5. Simulated removal of gcl
ian@pinguino:~$ sudo apt-get remove -s gcl [[sudo] password for ian: Reading package lists... Done Building dependency tree Reading state information... Done The following packages were automatically installed and are no longer required: linux-headers-2.6.31-14 linux-headers-2.6.31-14-generic libreadline5 Use 'apt-get autoremove' to remove them. The following packages will be REMOVED: gcl 0 upgraded, 0 newly installed, 1 to remove and 30 not upgraded. Remv gcl [2.6.7-45ubuntu1] |
Notice that the libreadline5 package that we installed as a prerequisite
for gcl is not removed automatically, although one of the output lines
tells us that this package, along with two Linux header packages, is no
longer required. The autoremove function of
apt-get (or the equivalent
remove function and the
--auto-remove option) will remove the requested
packages, along with any packages that were installed as dependencies but
are no longer required by any installed packages. This includes
dependencies installed by packages other than the one or ones you are
trying to remove, such as the linux-headers-2.6.31-14 and
linux-headers-2.6.31-14-generic packages in our example. Listing 6 shows
how to remove gcl, its dependency libreadline5, and the two unrelated
Linux header packages that are no longer required.
Listing 6. Removing gcl and dependencies
ian@pinguino:~$ sudo apt-get autoremove gcl Reading package lists... Done Building dependency tree Reading state information... Done The following packages will be REMOVED: gcl libreadline5 linux-headers-2.6.31-14 linux-headers-2.6.31-14-generic 0 upgraded, 0 newly installed, 4 to remove and 30 not upgraded. After this operation, 239MB disk space will be freed. Do you want to continue [Y/n]? y (Reading database ... 142327 files and directories currently installed.) Removing gcl ... remove/gcl: purging byte-compiled files for emacs22 remove/gcl: purging byte-compiled files for emacs23 Removing libreadline5 ... Removing linux-headers-2.6.31-14-generic ... Removing linux-headers-2.6.31-14 ... Processing triggers for man-db ... Processing triggers for libc-bin ... ldconfig deferred processing now taking place |
If you use the autoremove function of
apt-get but do not specify any package name,
then all unused packages that were installed as dependencies will be
removed from your system. You can also use the
apt-get purge option to remove
configuration information. See the man page for more information.
If you need to update an individual package, use
apt-get with the
install option again. Listing 7 shows how to
update the already installed tzdata package on my system. Remember to run
apt-get update before updating packages
to make sure your local database reflects the latest available
updates.
Listing 7. Updating a single package
ian@pinguino:~$ sudo apt-get install tzdata [sudo] password for ian: Reading package lists... Done Building dependency tree Reading state information... Done The following packages will be upgraded: tzdata 1 upgraded, 0 newly installed, 0 to remove and 29 not upgraded. Need to get 679kB of archives. After this operation, 0B of additional disk space will be used. Get:1 http://us.archive.ubuntu.com karmic-updates/main tzdata 2010i-0ubuntu0.9.10 [679kB] Fetched 679kB in 1s (569kB/s) Preconfiguring packages ... (Reading database ... 124394 files and directories currently installed.) Preparing to replace tzdata 2010h-0ubuntu0.9.10 (using .../tzdata_2010i-0ubuntu0.9.10_all .deb) ... Unpacking replacement tzdata ... Setting up tzdata (2010i-0ubuntu0.9.10) ... Current default time zone: 'America/New_York' Local time is now: Mon May 3 16:11:57 EDT 2010. Universal Time is now: Mon May 3 20:11:57 UTC 2010. Run 'dpkg-reconfigure tzdata' if you wish to change it. |
Updating all packages or upgrading to a new distribution
Rather than updating individual packages, you can update all packages on
your system using the apt-get upgrade
command. Similarly, apt-get dist-upgrade
will help you migrate to a new level of your distribution.
For more information on other capabilities and options for
apt-get, see the man page.
APT configuration—the apt.conf file
If you check the man page for apt-get, you will find that there are many
options. If you use the apt-get command a lot and find the default
options are not to your liking, you can set new defaults in
/etc/apt/apt.conf. A program, apt-config, is
available for scripts to interrogate the apt.conf file. See the man pages
for apt.conf and apt-config for further information.
APT includes a capability called debconf, which is used to configure
packages after they are installed. Packages that use this capability (and
not all do) can be reconfigured after they are installed. The easiest way
to do this is to use the dpkg-reconfigure
command. For example, the adduser command may create home directories that
are readable by all system users. You may not want this for privacy
reasons. Similarly, the tzdata package that we upgraded in Listing 7
suggested running
dpkg-reconfigure tzdata to change the
time zone. You must run dpkg-reconfigure with
root authority.
Figure 1 shows the first question you will be asked if you run
dpkg-reconfigure tzdata. The preset
default may not be America; it will reflect your own system.
Navigate around this text-mode screen using the Tab key
and the cursor movement keys.
Figure 1. Using dpkg-reconfigure to reconfigure time zone
Now let's look at some tools for getting information about packages. Some of these tools do other things as well, but we'll focus here on how to get information.
Another tool that is part of the APT system is the
dpkg tool. This is a medium-level package
management tool that can install and remove packages as well as
display status information. Configuration of dpkg can be controlled by
/etc/dpkg/dpkg.cfg, and you may also have a .dpkg.cfg file in
your home directory to provide further configuration.
The dpkg tool uses many files in the /var/lib/dpkg tree in your filesystem.
In particular, the file /var/lib/dpkg/status contains status information
about packages on your system. Listing 8 shows the use of
dpkg -s to display the status of the tzdata
package after we updated it and the gcl package after we removed it. Note
that the gcl package still shows some config files as remaining. You can
also use the purge option to purge
downloaded package files from the cache and remove configuration
information.
Listing 8. Tzdata package status
ian@pinguino:~$ dpkg -s gcl tzdata
Package: gcl
Status: deinstall ok config-files
Priority: optional
Section: interpreters
Installed-Size: 152848
Maintainer: Ubuntu MOTU Developers <ubuntu-motu@lists.ubuntu.com>
Architecture: i386
Version: 2.6.7-45ubuntu1
Config-Version: 2.6.7-45ubuntu1
Depends: libc6 (>= 2.7), libgmp3c2, libice6 (>= 1:1.0.0), libncurses5 (>= 5.6+20071006-3
), libreadline5 (>= 5.2), libsm6, libx11-6, libxaw7, libxext6, libxmu6, libxt6, tcl8.4 (
>= 8.4.16), tk8.4 (>= 8.4.16), debconf (>= 1.2.0), gcc, emacs22 | emacsen
Suggests: gcl-doc
Conffiles:
/etc/default/gcl 9301be50652f86b8d3f8b835f6dce03e
/etc/emacs/site-start.d/50gcl.el 12116c8c8988326764799973a0a7d5ab
Description: GNU Common Lisp compiler
GNU Common Lisp (GCL) is a Common Lisp compiler and interpreter
implemented in C, and complying mostly with the standard set
forth in the book "Common Lisp, the Language I". It attempts
to strike a useful middle ground in performance and portability
from its design around C.
.
This package contains the Lisp system itself. Documentation
is provided in the gcl-doc package.
Original-Maintainer: Camm Maguire <camm@enhanced.com>
Package: tzdata
Status: install ok installed
Priority: required
Section: libs
Installed-Size: 6276
Maintainer: Ubuntu Developers <ubuntu-devel-discuss@lists.ubuntu.com>
Architecture: all
Version: 2010i-0ubuntu0.9.10
Replaces: libc0.1, libc0.3, libc6, libc6.1
Provides: tzdata-squeeze
Depends: debconf (>= 0.5) | debconf-2.0
Description: time zone and daylight-saving time data
This package contains data required for the implementation of
standard local time for many representative locations around the
globe. It is updated periodically to reflect changes made by
political bodies to time zone boundaries, UTC offsets, and
daylight-saving rules.
Original-Maintainer: GNU Libc Maintainers <debian-glibc@lists.debian.org>
|
Packages and the files in them
You will often want to know what is in a package or what package a
particular file came from. These are both tasks for dpkg. Listing 9
illustrates the use of dpkg -L to list the
files (including directories) installed by the libparted package. For most
packages, you can just give the package name and not worry about specifying
a particular version. However, some packages may be available in multiple
versions, so you may need to specify a more detailed package name when
using dpkg to interrogate the package
information.
Listing 9. What is in the libparted package?
ian@pinguino:~$ dpkg -L libparted
Package `libparted' is not installed.
Use dpkg --info (= dpkg-deb --info) to examine archive files,
and dpkg --contents (= dpkg-deb --contents) to list their contents.
ian@pinguino:~$ dpkg -L libparted1.8-12
/.
/lib
/lib/libparted-1.8.so.12.0.0
/usr
/usr/share
/usr/share/doc
/usr/share/doc/libparted1.8-12
/usr/share/doc/libparted1.8-12/copyright
/usr/share/doc/libparted1.8-12/changelog.Debian.gz
/lib/libparted-1.8.so.12 |
To find which package contains a specific file, use the
-S option of dpkg, as shown in Listing 10. The
name of the package is listed on the left.
Listing 10. What package contains a file?
ian@pinguino:~$ dpkg -S /lib/libparted-1.8.so.12
libparted1.8-12: /lib/libparted-1.8.so.12 |
Sometimes a file may not appear to belong to any package. When
this occurs, you may need to do some extra sleuthing to find where a
package comes from. For example, the installation setup step may perform
tasks such as creating symbolic links that are not listed as part of the
package contents. A relatively recent addition to Linux systems is the
alternatives system, which is managed using the
update-alternatives command.
Alternatives are frequently created for commands such as
java, which might be the openJDK, Sun or IBM
version, among other possibilities.
Listing 11 shows how to use the which command to find
what is invoked if we try to run java. Then we
use the ls command to see what that
java command is symbolically linked to. The
link to the /etc/alternatives directory is a tip-off that we are using the
alternatives system, so we use the
update-alternatives command to find more
information and finally we use the
dpkg
-S command to confirm
that the java command comes from the
openjdk-6-jre-headless. The setup for the alternatives system would have
been done by a post-install script that is part of the
openjdk-6-jre-headless package.
Listing 11. A more complex use of dpkg -S
ian@pinguino:~$ which java
/usr/bin/java
ian@pinguino:~$ ls -l $(which java)
lrwxrwxrwx 1 root root 22 2010-05-03 17:51 /usr/bin/java -> /etc/alternatives/java
ian@pinguino:~$ update-alternatives --display java
java - auto mode
link currently points to /usr/lib/jvm/java-6-openjdk/jre/bin/java
/usr/lib/jvm/java-6-openjdk/jre/bin/java - priority 1061
slave java.1.gz: /usr/lib/jvm/java-6-openjdk/jre/man/man1/java.1.gz
Current `best' version is /usr/lib/jvm/java-6-openjdk/jre/bin/java.
ian@pinguino:~$ dpkg -S /usr/lib/jvm/java-6-openjdk/jre/bin/java
openjdk-6-jre-headless: /usr/lib/jvm/java-6-openjdk/jre/bin/java
|
Earlier, we mentioned that the status for packages is kept in
/var/lib/dpkg/status. We also mentioned that dpkg could do more than just
display package information. Now let's look at the
aptitude command, which provides a text-based
full-screen interface (using ncurses) to the APT package management
functions. You can use aptitude to install or remove packages as well as
to control status flags that indicate whether packages should be kept
up-to-date or held in their present state, for example. If you run the
aptitude command (as root), you see a
screen similar to Figure 2.
Figure 2. Running aptitude
Press Enter to expand or collapse the various selections,
then use ctrl-t to access the menu bar. Figure 3 shows
that a new kernel version, 2.6.31.20, is available for my system, among
other available updates. The 'i' in the left column indicates that the
current status is to install the package. The Help menu item explains the
various options you have, including holding a package at its current level
rather than updating it, removing it, or marking it as being automatically
installed and thus eligible for automatic removal.
Remember the autoremove option of
apt-get? Now you know how to examine or control
which packages are eligible for automatic removal. Use the keyboard
shortcuts described in the Help or use the
Package menu item to change the flags.
Figure 3. Running aptitude and examining package flags
You can use the slash ("/") key to search for packages. For example, if you wanted to reinstall the gcl package that we removed earlier, simply type "/gcl" to search for it. If the search takes you to something else with gcl in it, such as gcl-doc, press the "n" key to advance to the next match. Then use the Package menu to mark the package for installation.
When you are finished, select Actions->Install/remove packages (or press "g") to apply your selections to the system. You can also select the quit option if you do not want to apply the changes.
For help at any time, use the menu bar or type "?" (question mark) for help, and then press the "q" key to exit the help.
Upgrading Debian with other tools
You have now seen that aptitude can help you install or remove individual packages as well as upgrade all the packages on your system to the latest level.
In addition to aptitude, there are several other interactive package management interfaces for Debian systems, including dselect, synaptic, update-manager, gnome-apt, and wajig. Synaptic is a graphical application for use with the X Window System. Figure 4 shows the synaptic user interface with our old friend, the gcl package, marked for installation.
Figure 4. Installing gcl using synaptic
The Apply button will install gcl and update any other packages that are scheduled for update. The Reload button will refresh the package lists. If you are accustomed to GUI interfaces, you may find synaptic easier to use than apt-get, dpkg, or dselect.
Similarly, you may find that your system includes
update-manager, an X Window System application,
specifically tailored to help you keep your system up-to-date. If
installed, it is likely to be started automatically on a regular basis, so
that you don't forget to update.
Figure 5 shows how update manager displays the set of
updates that you saw in Figure 2. As was the case with
aptitude, the updates are classified so you know which updates are
important security updates.
Figure 5. Update Manager example
In our final topic on Debian package management, we look at ways to
find packages. Usually, apt-get and the other tools discussed here will
already know about any Debian package you might need from the list of
available packages. A command that we haven't used yet is
apt-cache, which is useful for searching
package information on your system. apt-cache can search using regular
expressions (see Learn Linux, 101: Search text
files using regular expressions for more information on regular
expressions). Suppose you wanted to find the name of the package containing
the Linux loader. Listing 12 shows how you might accomplish this.
Listing 12. Searching for the Linux loader with apt-cache
ian@pinguino:~$ apt-cache search "linux loader"
lilo - LInux LOader - The Classic OS loader can load Linux and others
lilo-doc - Documentation for LILO (LInux LOader)
|
You saw earlier that aptitude and synaptic also offer search tools. If you use synaptic, note that you have options on the search menu for searching only package names or package descriptions as well.
If you still can't find the package, you may be able to find it among the list of packages on the Debian site (see Resources for a link), or elsewhere on the Internet.
Most of the package tools can tell you a lot more about an installed package than about one that you do not yet have installed, such as the list of files within a package. If you need to find what package contains a program that you do not have installed, there are a few ways:
- You can guess what package might contain it and download the package without installing. Once you have the package, you can interrogate it.
- You can search the Internet.
- You can try the command-not-found capability, which is described under "Command not found" later in this article.
The apt-get command has a
-d option to download a package and not install
it. There is also a --print-uris option to show
where a package would be downloaded from and what its checksum would
be. Current checksums are likely to be SHA256 checksums, so you can check
the integrity of the downloaded package using the sha256sum command. Note
that the URI and checksum information are not displayed if you have
already downloaded the package, so you should get this information before
downloading the package.
Suppose you want to know whether the gcl command is really contained in the
gcl package. Listing 13 shows you how to use
apt-get to just download the gcl package
without installing it.
Listing 13. Using apt-get for download-only
ian@pinguino:~$ sudo apt-get install -d gclReading package lists... Done Building dependency tree Reading state information... Done The following extra packages will be installed: libreadline5 Suggested packages: gcl-doc The following NEW packages will be installed: gcl libreadline5 0 upgraded, 2 newly installed, 0 to remove and 0 not upgraded. Need to get 47.1MB of archives. After this operation, 157MB of additional disk space will be used. Do you want to continue [Y/n]? Get:1 http://us.archive.ubuntu.com karmic/main libreadline5 5.2-6 [140kB] Get:2 http://us.archive.ubuntu.com karmic/universe gcl 2.6.7-45ubuntu1 [47.0MB] Fetched 47.1MB in 7s (6,475kB/s) Download complete and in download only mode |
Once you have the package downloaded, you can use the
--info option of
dpkg to display the package information, or the
--contents option to show what files the
package installs. The downloaded file will be usually be located in
/var/cache/apt/archives/. Listing 14 shows how to locate the file you
downloaded and find out what binaries it will install (assuming they are
installed in a .../bin/... directory).
Listing 14. Using dpkg to list the contents of a .deb
ian@pinguino:~$ sudo find /var/cache -name "*.deb" /var/cache/apt/archives/gcl_2.6.7-45ubuntu1_i386.deb /var/cache/apt/archives/libreadline5_5.2-6_i386.deb ian@pinguino:~$ sudo dpkg --contents /var/cache/apt/archives/gcl*.deb| grep "/bin/" drwxr-xr-x root/root 0 2008-12-06 07:42 ./usr/bin/ -rwxr-xr-x root/root 617 2008-12-06 07:42 ./usr/bin/gcl |
If you do find and download a .deb file using
something other than apt-get, you can install
it using dpkg -i.
If you decide you do not want to install the package you downloaded into
the APT archives, you can run
apt-get clean to clear out any
downloaded package files.
If all else fails, there is another possible source for packages. Suppose
you find a program packaged as an RPM rather than a .deb. You may be able
to use the alien program, which can convert
between package formats. You should read the alien documentation carefully
as not all features of all package management systems can be converted to
another format by alien.
Back in Listing 1, you saw a helpful message telling you what package to
install to get the gcl command. How is this done? When the Bash shell
searches for a command and does not find it, then the shell searches for
a shell function named command_not_found_handle. Listing 15 shows how this
is defined on my Ubuntu 9.10 system.
Listing 15. command_not_found_handle
ian@pinguino:~$ type command_not_found_handle
command_not_found_handle is a function
command_not_found_handle ()
{
if [ -x /usr/lib/command-not-found ]; then
/usr/bin/python /usr/lib/command-not-found -- $1;
return $?;
else
return 127;
fi
} |
If the command_not_found_handle function exists, it is invoked with the
original command and original arguments as its arguments, and the
function's exit status becomes the exit status of the shell. If the
function is not defined, the shell prints an error message and returns an
exit status of 127. The function is usually set in the system
/etc/bash.bashrc file. You can see from Listing 15 that the function
checks for the existence of /usr/lib/command-not-found and runs it as a
Python script if it exists. If it does not exist, perhaps because the
command-not-found package that supplies it was removed after the shell
session was started, then the function mimics the standard system behavior
and returns 127.
No discussion of package installation would be complete without mentioning PackageKit, which is a system designed to make installing and updating software easier. The intent is to unify all the software graphical tools used in different distributions. PackageKit uses a system activated daemon, which means that the daemon is activated only when needed. Packagekit has version for Gnome (gnome-packagekit) and KDE KPackageKit).
There is a lot more to the Debian package management system than covered here. There is also a lot more to Debian than its package management system. See Resources for additional details and links to other articles in this series.
Learn
- Use the developerWorks roadmap for
LPIC-1 to find the developerWorks articles to help you study for
LPIC-1 certification based on the April 2009 objectives.
- At the LPIC
Program site, find detailed objectives, task lists, and sample
questions for the three levels of the Linux Professional Institute's Linux
system administration certification. In particular, see their April 2009
objectives for LPI exam 101 and LPI exam 102. Always refer to the LPIC Program site for the
latest objectives.
- Review the entire LPI exam prep series on
developerWorks to learn Linux fundamentals and prepare for system
administrator certification based on earlier LPI exam objectives prior to
April 2009.
- The Debian home page is your starting point for information about the
Debian distribution.
- Refer to the "Debian
installation guide" for more information on installing Debian.
- At Debian packages,
display and search Debian package lists.
- See the "APT HOWTO"
to learn more about the Debian package management
utility, APT.
- Check out the "Debian New Maintainers' Guide."
- Visit Ubuntu, Linux for Human Beings.
- See the PackageKit home
page to learn more about PackageKit.
- The Linux
Documentation Project has a variety of useful documents,
especially its HOWTOs.
-
In the developerWorks Linux zone,
find hundreds of how-to
articles
and tutorials, as well as downloads, discussion forums,
and a wealth other resources for Linux developers and administrators.
-
Stay current with
developerWorks technical events and webcasts focused on a variety of IBM products and IT industry topics.
-
Attend a free developerWorks Live!
briefing to get up-to-speed quickly on IBM products and tools as well as IT industry trends.
-
Watch developerWorks on-demand demos
ranging from product installation and setup demos for beginners, to advanced functionality for experienced developers.
-
Follow developerWorks on Twitter, or subscribe
to a
feed of Linux tweets on developerWorks.
Get products and technologies
- Get the Alien package
converter.
- Get Debian packages
from the Debian home page.
-
Evaluate IBM products
in the way that suits you best: Download a product trial, try a product online, use a product in a cloud environment, or spend a few hours in the
SOA Sandbox
learning how to implement Service Oriented Architecture efficiently.
Discuss
- Participate in the discussion forum.
-
Get involved in the My developerWorks community.
Connect with other developerWorks users while exploring the developer-driven blogs, forums, groups, and wikis.
Ian Shields works on a multitude of Linux projects for the developerWorks Linux zone. He is a Senior Programmer at IBM at the Research Triangle Park, NC. He joined IBM in Canberra, Australia, as a Systems Engineer in 1973, and has since worked on communications systems and pervasive computing in Montreal, Canada, and RTP, NC. He has several patents and has published several papers. His undergraduate degree is in pure mathematics and philosophy from the Australian National University. He has an M.S. and Ph.D. in computer science from North Carolina State University. Learn more about Ian in in Ian's profile on My developerWorks.
Table of contents
- Overview
- Introducing package management
- Installing Debian packages
- Package locations
- Removing Debian packages
- Updating Debian packages
- Reconfiguring Debian packages
- Debian package information
- Using aptitude
- Upgrading Debian with other tools
- Finding Debian packages
- Command not found
- PackageKit
- Resources
- About the author
- Comments
Local resources
Tags
Use the slider bar to see more or fewer tags.
For articles in technology zones (such as Java technology, Linux, Open source, XML), Popular tags shows the top tags for all technology zones. For articles in product zones (such as Info Mgmt, Rational, WebSphere), Popular tags shows the top tags for just that product zone.
For articles in technology zones (such as Java technology, Linux, Open source, XML), My tags shows your tags for all technology zones. For articles in product zones (such as Info Mgmt, Rational, WebSphere), My tags shows your tags for just that product zone.
Popular article tags |
My article tagsSkip to tags list
Popular article tags |
My article tags
