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Chapter 2. Debian fundamentals
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Currently all of the control files can be found in the directory /var/lib/dpkg/info. The
files relevant to package foo begin with the name “foo” and have file extensions of “preinst”,
“postinst”, etc., as appropriate. The file foo.list in that directory lists all of the files that
were installed with the package foo. (Note that the location of these files is a dpkg internal,
and may be subject to change.)
2.2.6
Package priorities
Each Debian package is assigned a priority by the distribution maintainers, as an aid to the
package management system. The priorities are:
• Required packages are necessary for the proper functioning of the system.
This includes all tools that are necessary to repair system defects. You must not remove
these packages or your system may become totally broken and you may not even be
able to use dpkg to restore things. Systems with only the Required packages are probably inadequate for most purposes, but they do have enough functionality to allow the
sysadmin to boot and install more software.
• Important packages should be found on any Unix-like system.
Other packages without which the system will not run well or be usable will carry this
priority. This does not include Emacs or X11 or TeX or any other large applications. These
packages only constitute the bare infrastructure.
• Standard packages are standard on any Linux system, including a reasonably small but
not too limited character-mode system.
This is what will install by default if users do not select anything else. “Standard” does
not include many large applications, but it does include Emacs (this is more a piece of
infrastructure than an application) and a reasonable subset of TeX and LaTeX (if this turns
out to be possible without X).
• Optional packages include all those that you might reasonably want to install even if
you are unfamiliar with them, and if you don’t have specialized requirements.
This includes X11, a full TeX distribution, and lots of applications.
• Extra packages either conflict with others with higher priorities, have little use to users
who are unfamiliar with them, or have specialized requirements that make them unsuitable for “Optional”.
Please note the differences among “Priority: required”, “Section: base” and “Essential: yes” in
the package description. “Section: base” means that this package is installed before everything
else on a new system. Most of the packages in “Section: base” have the “Priority: required” or
at least “Priority: important”, and many of them are tagged with “Essential: yes”. “Essential:
yes” means that this package requires to specify an extra force option to the package management system such as dpkg when removing from the system. For example, libc6, mawk, and
makedev are “Priority: required” and “Section: base” but are not “Essential: yes”.