In its basic form, aptitude's configuration file is a list of options and their values. Each line of the file should have the form “Option Value;”: for instance, the following line in the configuration file sets the option Aptitude::Theme to “Dselect”.

Aptitude::Theme "Dselect";

An option can “contain” other options if they are written in curly braces between the option and the semicolon following it, like this:

Aptitude::UI {
  Package-Status-Format "";
  Package-Display-Format "";
};

An option that contains other options is sometimes called a group. In fact, the double colons that appear in option names are actually a shorthand way of indicating containment: the option Aptitude::UI::Default-Grouping is contained in the group Aptitude::UI, which itself is contained in the group Aptitude. Thus, if you wanted to, you could set this option to "" as follows:

Aptitude {
  UI {
    Default-Grouping "";
  };
};

For more information on the format of the configuration file, see the manual page apt.conf(5).

aptitude's configuration is read from the following sources, in order:

When an option is being checked, these sources are searched in order, and the first one that provides a value for the option is used. For instance, setting an option in /etc/apt/apt.conf will override aptitude's defaults for that option, but will not override user settings in ~/.aptitude/config.

The following configuration options are used by aptitude. Note that these are not the only available configuration options; options used by the underlying apt system are not listed here. See the manual pages apt(8) and apt.conf(5) for information on apt options.