On Sun, 02 Jun 2013 17:41:21 -0700
Zac Medico <zmedico@gentoo.org> wrote:

I'll answer to some parts with what I think the user might think; I
know the answer to most of those, but the user might not.

> Beginning with sys-apps/portage-2.1.12, FEATURES=preserve-libs is
> enabled by default. This feature will preserve libraries when the
> sonames change during upgrade or downgrade.

Why are libraries being preserved?

> Libraries are preserved only if consumers of those libraries are
> detected.

When exactly are those consumers detected?

> Preserved libraries are automatically removed when there are no
> remaining consumers.

When exactly does this happen? At the end of any emerge action?

> Run `emerge @preserved-rebuild` in order to rebuild all consumers of
> preserved libraries.

When and why? Do I run this once? Do I need to run this often?

Besides these questions, the transition from revdep-rebuild to
@preserved-rebuild may be worth a note as well; if I remember correctly
you have to do one last revdep-rebuild when you enable this feature, or
in other words preserve-libs won't detect present inconsistencies. I
feel like this should probably be documented as well, as part of
mentioning that this is intended to replace revdep-rebuild...

-- 
With kind regards,

Tom Wijsman (TomWij)
Gentoo Developer

E-mail address  : TomWij@gentoo.org
GPG Public Key  : 6D34E57D
GPG Fingerprint : C165 AF18 AB4C 400B C3D2  ABF0 95B2 1FCD 6D34 E57D