Slotting

Packages can support having multiple versions installed simultaneously. This is useful for libraries which may have changed interfaces between versions — for example, the gtk+ package can install both versions 1.2 and 2.6 in parallel. This feature is called slotting.

Most packages have no need for slotting. These packages specify SLOT="0" in the ebuilds. This is not the same as specifying an empty slot — an empty slot means "disable slotting entirely", and should not be used.

Portage permits at most one instance of a package installation per SLOT value. For example, say we have the following:

• foo-1.1 with SLOT="1"
• foo-1.2 with SLOT="1"
• foo-2.0 with SLOT="2"
• foo-2.1 with SLOT="2"

Then the user could have, say, foo-1.2 and foo-2.0 installed in parallel, but not foo-1.1 and foo-1.2. Note that it is entirely possible that the user may have foo-2.0 installed and no foo-1.x at all.

It is not possible to DEPEND upon a package in a specific slot.

Currently portage will accept an arbitrary string for the value of SLOT. For future compatibility, it is recommended that slots contain only characters which are allowed in an ebuild name or version (alphanumerics, hypens, full stops, underscores, the plus character) — other characters may cause problems with future portage enhancements.