World set (Portage)

The world set, also referred to as @world in Portage development, encompasses the system set and the selected set.

Packages belonging to the world set are listed by default into the file.

It is the world file, together with the profile and (including ) settings, that defines what software is installed on a system using Portage.

Later, when a world update is requested (through or similar command), Portage will use the world file as the base for its update calculations.

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

Keep it clean
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.

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 --depclean 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:

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

External resources

 * https://forums.gentoo.org/viewtopic-t-1042252-start-11.html Forum thread