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Chapter 2. Debian fundamentals
2.3.2
19
APT
APT (the Advanced Packaging Tool) is an advanced interface to the Debian packaging system consisting of several programs whose names typically begin with “apt-”. apt-get,
apt-cache, and apt-cdrom are the command-line tools for handling packages. These also
function as the user’s “back end” programs to other tools, such as dselect and aptitude.
Currently aptitude is the preferred tool for system maintenance.
For more information, install packages apt and aptitude and read aptitude(8),
apt-get(8), apt-cache(8), apt-cdrom(8), apt.conf(5), sources.list(5), and
apt_preferences(5).
An alternative source of information is the APT HOWTO (http://www.debian.org/doc/
manuals/apt-howto/). This can be installed by apt-howto at file: ///usr/share
/doc/Debian/apt-howto/.
apt-get upgrade and apt-get dist-upgrade pull only the packages listed under “Depends:” and overlook all the packages listed under “Recommends:” and “Suggests:”. To avoid
this, use dselect.
2.3.3 dselect
This program is a menu-driven user interface to the Debian package management system. It
is particularly useful for first-time installations and large-scale upgrades. See ‘dselect’ on
page 80.
For more information, read dselect Documentation for Beginners (http://www.debian.
org/releases/woody/i386/dselect-beginner).
2.3.4
Upgrading a running system
The kernel (filesystem) in Debian systems supports replacing files even while they’re being
used. When packages are upgraded any services provided by those packages are restarted if
they are configured to run in the current runlevel. The Debian system does not require use of
the single-user mode to upgrade a running system.
2.3.5
Downloaded and cached .deb archive files
If you have manually downloaded package files to your disk (which is not absolutely necessary, see above for the description of dpkg-ftp or APT), then after you have installed the
packages, you can remove the .deb files from your system.
If APT is used, these files are cached in the /var/cache/apt/archives directory. You
may erase them after installation (apt-get clean) or copy them to another machine’s /var
/cache/apt/archives directory to save downloading during subsequent installations.