Preserved-rebuild

@preserved-rebuild is Article description::a [[Portage set.]] During library updates, the old version of the library is often being kept because other packages are still being built against this library. could solve this by updating all these packages that are still built against the old version. However, this can have undesired effect like a long installation time when updating a library. So does not update the depending libraries, but put them into a set instead: @preserved-rebuild.

After finishing a library update, it is possible to clean up the old library version via: