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...making Linux just a little more fun! |
By Rob Tougher |
I use the Debian GNU/Linux operating system. I use Debian for the following reasons:
I install Debian software using APT, the Advanced Packaging Tool. With APT I can install Debian software from either a CD-ROM, an FTP server, an HTTP server, or my local filesystem. What's even better is that Debian provides their software archives on freely-accessible FTP and HTTP servers. Installation is as simple as pointing APT at one of these servers and telling it to run.
The purpose of this article is to give you an overview of APT and describe the basic commands for using it. My hope is that this article will show you how easy software installation can be using APT.
The main concept in APT is the package. Every software application that
Debian provides has a corresponding package. A package is a file
with a *.deb extension and includes these items:
All operations in APT deal with packages. When you want to install a software application, you tell APT to install that application's package. When you want to remove a software application, you tell APT to remove that application's package. Even if you only want information about the software application, you need to ask APT for the information using the application's package name.
Another important concept is the package cache. The package cache is a complete list of available packages in the Debian distribution. The package cache is stored on your local machine, and you are responsible for keeping it updated. A later section deals with updating your package cache.
Before you can use APT you have to tell it where to look for package files. Each location you specify is called a source. A source can be a CD-ROM, an HTTP server, an FTP server, or an archive on your hard drive.
APT looks in /etc/apt/sources.list for your list of sources.
The following is my sources.list file:
deb http://security.debian.org/ stable/updates main deb http://http.us.debian.org/debian stable main contrib non-free deb cdrom:[Debian GNU/Linux 3.0 r0 _Woody_ - Official i386 Binary-6 (20020718)]/ unstable contrib main non-US/contrib non-US/main deb cdrom:[Debian GNU/Linux 3.0 r0 _Woody_ - Official i386 Binary-7 (20020718)]/ unstable contrib main non-US/contrib non-US/main deb cdrom:[Debian GNU/Linux 3.0 r0 _Woody_ - Official i386 Binary-5 (20020718)]/ unstable contrib main non-US/contrib non-US/main deb cdrom:[Debian GNU/Linux 3.0 r0 _Woody_ - Official i386 Binary-4 (20020718)]/ unstable contrib main non-US/contrib non-US/main deb cdrom:[Debian GNU/Linux 3.0 r0 _Woody_ - Official i386 Binary-3 (20020718)]/ unstable contrib main non-US/contrib non-US/main deb cdrom:[Debian GNU/Linux 3.0 r0 _Woody_ - Official i386 Binary-2 (20020718)]/ unstable contrib main non-US/contrib non-US/main deb cdrom:[Debian GNU/Linux 3.0 r0 _Woody_ - Official i386 Binary-1 (20020718)]/ unstable contrib main non-US/contrib non-US/main
Adding HTTP, FTP, and local file archives to sources.list is simple -
you can add the entries into the file using a text editor (Debian keeps a list
of mirrors on their web site).
To add CD-ROMs you have to use the apt-cdrom command:
prompt$ apt-cdrom add
You are responsible for keeping your local package cache updated. Every time you want to install or upgrade a software application, you should update your package cache first. This ensures that you have the latest information about the software you are installing.
Run this command to update your package cache:
prompt$ apt-get update
The apt-cache utility allows you to search the local package cache for packages with certain text in it.
For example, you might want to install the Apache HTTP server on your machine. You could search for the Apache package using the following command:
prompt$ apt-cache search apache
This command returns 119 packages on my machine. Instead of reading
through all of the entries, you could filter the output using
grep:
prompt$ apt-cache search apache | grep "^apache"
This command generates the following:
apache-doc - Apache web server docs apache-dev - Apache web server development kit apache-ssl - Versatile, high-performance HTTP server with SSL support apache-common - Support files for all Apache web servers apache - Versatile, high-performance HTTP server apache-perl - Versatile, high-performance HTTP server with added Perl support
After having searched for a package, you might want to view the
information for that package. The apt-cache utility takes
a show command, like the following:
prompt$ apt-cache show packagename
For example, If you wanted to view the information for the apache
package, you would type the following at a command prompt:
prompt$ apt-cache show apache
This returns the following:
Package: apache
Priority: optional
Section: web
Installed-Size: 748
Maintainer: Matthew Wilcox <[email protected]>
Architecture: i386
Version: 1.3.26-0woody1
Replaces: apache-modules
Provides: httpd
Depends: libc6 (>= 2.2.4-4), libdb2 (>= 2:2.7.7.0-7), libexpat1 (>= 1.95.2-6), mime-support, apache-common (>= 1.3.26-0), apache-common (<< 1.3.27-0), perl5 | perl, logrotate (>= 3.5.4-1), dpkg (>> 1.9.0)
Suggests: apache-doc
Conflicts: apache-modules, libapache-mod-perl (<= 1.17-1), jserv (<= 1.1-3)
Filename: pool/main/a/apache/apache_1.3.26-0woody1_i386.deb
Size: 352814
MD5Sum: 728257f5de8d71e0d00701bdca9d452d
Description: Versatile, high-performance HTTP server
The most popular server in the world, Apache features a modular
design and supports dynamic selection of extension modules at runtime.
Some of its strong points are its range of possible customization,
dynamic adjustment of the number of server processes, and a whole
range of available modules including many authentication mechanisms,
server-parsed HTML, server-side includes, access control, CERN httpd
metafiles emulation, proxy caching, etc. Apache also supports multiple
virtual homing.
.
Separate Debian packages are available for PHP3, mod_perl, Java
Servlet support, Apache-SSL, and other common extensions. More
information is available at http://www.apache.org/.
Task: web-server
Installing a package is achieved using the apt-get utility.
The following will install a package:
prompt$ apt-get install packagename
Typing the following at a command prompt would install the Apache HTTP Server on your machine:
prompt$ apt-get install apache
You can remove packages from your machine with the following command:
prompt$ apt-get remove packagename
For example, if you wanted to remove the Apache HTTP Server from your machine, you would use the following:
prompt$ apt-get remove apache
It's good to keep your system updated with the latest (stable) versions of software. Doing this using APT is a simple two-step operation. You have to do only the following:
prompt$ apt-get update prompt$ apt-get upgrade
The first command updates your local package cache (we saw this in a previous section). The second command upgrades any packages installed on your machine that have newer versions available.
In this article I described the basic usage of APT. You should now be able to use APT to install Debian software on your machine.