Ludovic Courtès <ludovic.cour...@inria.fr> writes:
Hi!
Ricardo Wurmus <rek...@elephly.net> skribis:
There are two problems here:
1) I don’t think “guix gc --list-dead” (or “--list-live”, or
more
generally “findRoots” in nix/libstore/gc.cc) should delete
anything. It should just list and not clean up.
Maybe ‘findRoots’ could populate the list of stale roots and
it’d be up
to the caller to decide whether to delete them or not?
Yes, this would be better. It already does this for links whose
targets exist but cannot be read.
2) For cluster installations with remote file systems perhaps
there’s
something else we can do to record gcroots. We now have this
excursion into unreadable space because we use a symlink, but
the
start ($localstatedir/gcroots/auto) and endpoints
(/gnu/store/…) are
both accessible by the daemon. Since these intermediate
locations are
tied to user accounts, could we not store them in a per-user
directory?
This problem does not exist for user profiles, because the link
in
unreadable home directories is not all that important; it
merely
points to $localstatedir, which is always readable by the
daemon. Perhaps we could do the same for temporary roots and
let
*users* decide when to let go of them by giving them a command
to
erase the important links in $localstatedir.
So instead of having a link from
/gnu/var/guix/gcroots/auto/8ypp8dmwnydgbsgjcms2wyb32mng0wri to
/home/me/projects/mrg1_chipseq/.guix-profile-1-link pointing to
/gnu/store/ap0vrfxjdj57iqdapg8q83l4f7aylqzm-profile, we would
record
/var/guix/profiles/per-user/me/auto/8ypp8dmwnydgbsgjcms2wyb32mng0wri
pointing to
/gnu/store/ap0vrfxjdj57iqdapg8q83l4f7aylqzm-profile, and
then point /home/me/projects/mrg1_chipseq/.guix-profile-1-link
at
that. Yes, removing
/home/me/projects/mrg1_chipseq/.guix-profile-1-link would no
longer free up the profile for garbage collection, but removing
$(readlink /home/me/projects/mrg1_chipseq/.guix-profile-1-link)
would.
Yes, but how would per-user/me/auto/* be cleaned up?
Yeah, that’s an open question.
I get the appeal of having these things be cleaned up
automatically when the link disappears, but if we added this extra
layer of indirection for cluster deployments this would become
manual.
Can we make this configurable perhaps…? On my cluster
installation I’d rather have a cron job to erase the stuff in
per-user/me/auto/* on my own terms, than to have “guix gc” fail to
resolve links and consider it all garbage.
--
Ricardo
