Datasheet

91
Chapter 4 Software Management
As you can see, the packages that were installed alongside mutt were also removed
when you asked for
mutts removal. This is because you installed it with aptitude,
removed it with
aptitude, and mutt was the only installed package that declared
dependencies on these packages. If another package had required, say,
mime-
support
, the mime-support package would have been left intact. Unfortunately,
aptitude can only know whether other packages need a given package. You may
have, after installing a package automatically to satisfy a dependency, started using
the package directly, so be careful and read
aptitudes output before telling it
to go ahead with the operation. If you want to keep some of those automatically
installed packages, one way to do it is to use aptitude’s fullscreen interactive
interface.
So, as usual, fire up
aptitude. Press / to start a search, type elinks, and press
Enter.
elinks should be highlighted. To mark a highlighted package for removal,
press the minus/dash key (
-). To purge it, type in an underscore (_). For this exam-
ple, you want to purge
elinks, so type an underscore. You’ll note that the line
once again changes color, this time to purple. Press the G key to go to the summary
screen, and you’ll see that both
liblua50 and liblualib50 are also going to be
uninstalled. Suppose you’d like to keep
liblua50 around. Highlight that package
and press
+, the same key you would use to mark a package for installation. The
color of the line changes back to normal, and now
liblua50 won’t be removed. If
you want to mark packages as automatically or manually installed, highlight the
packages and press
M or m, respectively. Press the minus key to mark liblua50 for
removal again, and then press G to start the operation. When you’re done, quit
aptitude.
Configuring and Configuration Files
There are two forms of configuration on a Debian system: application-specific config-
uration and
debconf-based configuration. Application-specific configuration typi-
cally means that the configuration for programs is stored in configuration files.
Changing or customizing this type of configuration usually means editing a configu-
ration file by hand and changing or adding variables and values. Debian attempts
to make package installation painless, and most package maintainers avoid using
interactive
debconf prompts during a package install, but sometimes it’s unavoid-
able. If a package can’t provide a sensible default configuration file, it will instead
ask some
debconf questions. The advantage of debconf is that the user can decide
what sorts of questions he’d like to see, and how to see them.
Configuring packages using debconf
debconf is the standard Debian configuration system. Many packages use debconf
to provide a single interface to configuration that eliminates the need to have users
edit files by instead providing sane defaults and a way to prompt users with ques-
tions.
debconf questions are generally asked as part of the package’s installation,
09_576445 ch04.qxd 7/5/05 3:10 PM Page 91