When it starts, aptitude shows a list of packages sorted by state (installed, non-installed, or installed but not available on the mirrors — other sections display tasks, virtual packages, and new packages that appeared recently on mirrors). To facilitate thematic browsing, other views are available. In all cases, aptitude displays a list combining categories and packages on the screen. Categories are organized through a tree structure, whose branches can respectively be unfolded or closed with the Enter, [ and ] keys. + should be used to mark a package for installation, - to mark it for removal and _ to purge it (note than these keys can also be used for categories, in which case the corresponding actions will be applied to all the packages of the category). u updates the lists of available packages and Shift+u prepares a global system upgrade. g switches to a summary view of the requested changes (and typing g again will apply the changes), and q quits the current view. If you are in the initial view, this will effectively close aptitude.
DOCUMENTATION aptitude
This section does not cover the finer details of using aptitude, it rather focuses on giving you a survival kit to use it. aptitude is rather well documented and we advise you to use its complete manual available in the aptitude-doc-en package.
→ file:///usr/share/doc/aptitude/html/en/index.html
To search for a package, you can type / followed by a search pattern. This pattern matches the name of the package, but can also be applied to the description (if preceded by ~d), to the section (with ~s) or to other characteristics detailed in the documentation. The same patterns can filter the list of displayed packages: type the l key (as in limit) and enter the pattern.
6.4.1.1. Tracking Automatically Installed Packages
One of the essential functionnalities of aptitude (which has also been integrated to apt-get since Lenny) is the tracking of packages installed only through dependencies. These packages are called “automatic” and are tagged with an “A” in the list of packages — they often include libraries for instance. When a package is removed, the corresponding automatic packages are also selected for removal unless another “manually installed” package depends on them. It is possible to mark a package as automatic (with Shift+m) or to remove the mark (m key). When maintaining a system with aptitude, it is a good habit to mark as automatic any package that you don't need directly so that they are automatically removed when they aren't necessary anymore. You can either navigate the list of installed packages and play with Shift+m, or apply the flag to entire sections (for example the libs section). This habit can help you to keep your system tidy and offers a simple way to visualize the packages in use on a machine, without all the libraries and dependencies that you don't really care about. The related pattern that can be used with l (to activate the filter mode) is ~i!~M. It specifies that you only want to see installed packages (~i) not marked as automatic (!~M).
People might want to know why an automatically installed package is present on the system. To get this information from the command-line, you can use aptitude why package:
$ aptitude why python-debian
i aptitude Recommends apt-xapian-index
i A apt-xapian-index Depends python-debian (>= 0.1.15)
WORTH FOLLOWING Recent evolutions of apt-get and aptitude
Some of the advantages that aptitude historically had over apt-get have recently disappeared. For instance, since the release of Lenny, apt-get memorizes the packages that have been installed only to satisfy dependencies, just like aptitude has always done. It can also follow recommendations expressed by one package on another.
Among the recent evolutions of aptitude, a new version with a graphical interface is currently being developed. Even if it's available in Squeeze (in the separate aptitude-gtk package), it's not complete yet and is subject to stability issues.
TOOL Using aptitude on the command-line interface
Most of aptitude's features are accessible via the interactive interface as well as via command-lines. These command-lines will seem familiar to regular users of apt-get and apt-cache.
The advanced features of aptitude are also available on the command-line. You can use the same package search patterns as in the interactive version. For example, if you want to run the previously suggested cleanup of “automatic” packages, and if you know that none of the locally installed programs require any particular libraries or Perl modules, you can mark the corresponding packages as automatic with a single command:
# aptitude markauto '~slibs|~sperl'
Here, you can clearly see the power of the search pattern system of aptitude, which enables the instant selection of all the packages in the libs and perl sections.
Beware, if some packages are marked as automatic and if no other package depends on them, they will be removed immediately (after a confirmation request).
ALTERNATIVE deborphan and debfoster
Before aptitude came to life with its tracking of automatic packages, there were two utilities producing lists of unnecessary packages: deborphan and debfoster.
deborphan is the most rudimentary of both. It simply scans the libs and oldlibs sections (in the absence of supplementary instructions) looking for the packages that are currently installed and that no other packages depends on. The resulting list can then serve as a basis to remove unneeded packages.
debfoster has a more elaborate approach, very similar to aptitude's: it maintains a list of packages that have been explicitly installed, and remembers what packages are really required between each invocation. If new packages appear on the system and if debfoster doesn't know them as required packages, they will be shown on the screen together with a list of their dependencies. The program then offers a choice: remove the package (possibly together with those that depend on it), mark it as explicitly required, or ignore it temporarily.
6.4.1.2. Managing Recommendations, Suggestions and Tasks
Another interesting feature of aptitude is the fact that it respects recommendations between packages while still giving users the choice not to install them on a case by case basis. For example, the gnome-desktop-environment package recommends gnome-accessibility (among others). When you select the former for installation, the latter will also be selected (and marked as automatic if not already installed on the system). Typing g will make it obvious: gnome-accessibility appears on the summary screen of pending actions in the list of packages installed automatically to satisfy dependencies. However, you can decide not to install it by deselecting it before confirming the operations.