The dselect program is useful, because it
lets you browse a list of available packages, viewing their
descriptions and dependencies, and selecting desired packages for
installation. However, if you know the name of a package you want to
install, apt-get is often the easiest way to
install it. Before using apt-get, you must
configure the sources.list
file. This same file
is used when you choose the apt access method of
dselect. Even if you don’t plan on using
apt-get, you’ll find the information in the
following subsection useful.
The sources.list
file resides in the
/etc/apt
directory. Like most other Linux
configuration files, it can be revised by using an ordinary text
editor, such as ae.
The file contains a series of lines, each specifying a source for packages. The lines are consulted serially, so it’s usually advantageous to place lines that specify local sources—such as a CD-ROM—ahead of lines that specify remote sources. Doing so can save many minutes of download time.
Each line has the form:
deb uri distribution components
The uri
is a universal resource
identifier (URI) the specifies the computer on which the packages
reside, the location of the packages, and the protocol used for
accessing the packages. It has the following form:
protocol://host/path
Four protocols—sometimes called URI types—are recognized:
The host
part of the URI and the
preceding pair of slashes (//) are used only for the
http and ftp
protocols. There, the host
part of the URI
gives the name of the host that contains the packages.
The path
part of the URI always
appears, with the preceding slash (/). It specifies the absolute path
of the directory that contains the packages.
Here are some examples of typical URIs:
cdrom:/cdrom cdrom:/mnt/cdrom file:/mnt file:/debian http://www.us.debian.org/debian http://non-us.debian.org/debian-non-US ftp://ftp.debian.org/debian ftp://nonus.debian.org/debian-non-US
The distribution part of a sources.list
line specifies the distribution release that contains the
packages. Typical values include:
The latest stable release; that is, one that is commonly regarded as having sufficiently few serious bugs for everyday use.
The latest unstable release. This release sometimes contains serious bugs and should not be installed by users who require high levels of system availability or reliability.
The components part of a sources.list
line
specifies the parts of the distribution that will be accessed. Typical
values include:
A typical sources.list
file might contain
the following entries:
deb file:/cdrom stable main contrib deb http://www.us.debian.org/debian stable main contrib non-free deb http://non-us.debian.org/debian-non-US stable non-US
This configuration allows rapid access to the distribution packages contained on the local CD-ROM. It also allows convenient access via the network to other packages and more recent package versions stored on web servers.
Once you’ve configured sources.list, you can use apt-get to update information on available packages, to install a package, or to upgrade installed packages.
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