[gentoo-dev] Re: rfc: moving default location of portage tree

[Ulrich Mueller]

>>>>> On Wed, 18 Jul 2018, Christopher Head wrote:

> On July 18, 2018 2:55:55 AM PDT, Ulrich Mueller <ulm@g.o> wrote:
>> It was mentioned that all three directories (ebuild repository,
>> binary packages, distfiles) have some characteristics of a cache.
>> However, I think this is much more true for distfiles than for the
>> other two, which cannot be easily restored to a previous state.

> Neither can a Web browser’s cache, if the remote page has changed,
> yet those are still called caches. Surely a cache is something that
> can safely be discarded without negative impact

In my understanding, a cache is typically an open collection of items.
Some subset of them can be deleted without much negative consequence,
and there may also be surplus items that are no longer necessary and
will be expired at some later time in order to reclaim disk space.

Nothing of this is true for an ebuild repository, which is a closed
collection of files: A single file cannot be discarded without
invalidating the whole repository. Also there cannot be any stray
files which would be expired later. Same as above, a single stray file
will invalidate all.

(A collection of binary packages may qualify as a cache though, by
this definition.)

> (which, for most users, the ebuild tree can be, since for most
> users, getting back today’s tree rather than last week’s is not a
> negative impact), not something that can be restored to exactly its
> prior state automatically.

Consider a production system that is only updated at certain well
defined times. Its system administrator may still want to install one
additional package, or flip a use flag for another. In this scenario,
the gentoo repository is a precious resource, and restoring it to a
different state would not be acceptable.

Ulrich