Selected set (Portage)

The selected set, colloquially known as the world file, Article description::contains the packages the admin has explicitly installed. The selected set, together with the profile set and the system set, make up the world set. With a couple of exceptions, Portage will register selected set package atoms to the file.

Avoiding an atom in the world file
In order to avoid problems in dependency resolution when updating the system, the file should contain as few dependencies as possible. So use the   option for emerging dependencies.

Checking the world file
The command can be used to see if any problems exist in the world file:

Keeping the world file clean
Dependencies already listed in this file can be found using the command and be collected in a file say :

Entries collected in can be cross-checked using the   option:

The option will remove these entries without unmerging them.

In case indicates some needed or wanted package would be unmerged, those can be re-added using the  option. See the next section for details.

Adding an atom without recompilation
To add a package to the selected set without recompiling the package:

It will add the atom to the file without compiling it again.

External resources

 * https://forums.gentoo.org/viewtopic-t-1042252-start-11.html - A forum thread that discusses dependency calculation using the world file.