Now that you can move about the list of packages, it's time to start using aptitude to install and remove packages. In this section you will learn how to flag packages for installation, deletion, and upgrade.
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You can only change your system's setup as the |
All changes to a package are performed by first highlighting it in the package list, then pressing a key corresponding to the action which should be performed. The basic action keys [2] are + to install or upgrade a package, - to remove a package, and = to prevent a package from being automatically upgraded (this is known as holding the package). These actions are not performed immediately; aptitude will simply update the package list to show the change that has been requested.
For instance, in the screen shot below, the
kaffeine
package was selected and
+ was pushed. The package is now
highlighted in green and the letter “i” has
appeared to the left of its name, to indicate that it will
be installed; in addition, an estimate of the amount of
space that the package will use is displayed.
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At any time, you can use Control+u) to “undo” any change to one or more packages. This is very useful if an action has unforseen consequences and you want to “take it back”. -> ( |
In addition to actions that affect individual packages, another important action is available: typing U will attempt to upgrade any packages that can be upgraded. You should use this command on a regular basis to keep your system up-to-date.
Sometimes, changing a package's state will cause dependency
relationships to become unfulfilled; packages with
unfulfilled dependencies are said to be
broken. aptitude will warn you
when this happens, and explain why it occured. For
instance, here is what happens if you attempt to remove
libpopt0
:
As you can see, aptitude displays two indicators that
something has gone wrong: first, the number of broken
packages is displayed in the upper blue area; second, the
lower half of the display changes to describe broken
packages that are related to the currently highlighted
package. To quickly find broken packages in the package
list, you can search for ~b
.
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When there is more information in the lower half of the display than fits into the available space, the a and z keys can be used to scroll through it. |
If you do not resolve the situation on your own, aptitude will try to fix things for you when you commit your selections. However, it is hard to automatically solve dependency problems, and you may not be happy with the results, so it is generally better to solve problems such as this before committing your selections.
[2] You can also change packages using the menu; see the section called “The Package Menu” for details.