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authorLudovic Courtès <ludo@gnu.org>2017-11-12 21:41:34 +0100
committerLudovic Courtès <ludo@gnu.org>2017-11-12 22:42:17 +0100
commit6a98b9f34e6190a2e1d11bedd5853aa94cf25ca7 (patch)
tree61f67ecd21815464c76afa239cb247850ef2e92e
parent2560aa7adbfcb46306e8b19180bd48d39c2da6dc (diff)
downloadguix-6a98b9f34e6190a2e1d11bedd5853aa94cf25ca7.tar
guix-6a98b9f34e6190a2e1d11bedd5853aa94cf25ca7.tar.gz
doc: Better explain GC roots.
Fixes <https://bugs.gnu.org/24194>. Reported by J. Eppler <j.eppler@openmailbox.org>. * doc/guix.texi (Invoking guix-daemon): Add index entries for GC roots. Add xref to "Invoking guix gc". (Invoking guix gc): Add the string "GC roots"; mention /var/guix/gcroots. (Additional Build Options): Add index entries. Better explain --root. (Invoking guix environment): Add xref to "Invoking guix gc".
-rw-r--r--doc/guix.texi24
1 files changed, 20 insertions, 4 deletions
diff --git a/doc/guix.texi b/doc/guix.texi
index 11a9de6897..0bc2be1fd1 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -1236,9 +1236,12 @@ this optimization.
Tell whether the garbage collector (GC) must keep outputs of live
derivations.
+@cindex GC roots
+@cindex garbage collector roots
When set to ``yes'', the GC will keep the outputs of any live derivation
available in the store---the @code{.drv} files. The default is ``no'',
meaning that derivation outputs are kept only if they are GC roots.
+@xref{Invoking guix gc}, for more on GC roots.
@item --gc-keep-derivations[=yes|no]
Tell whether the garbage collector (GC) must keep derivations
@@ -2338,12 +2341,16 @@ collector to reclaim space from the @file{/gnu/store} directory. It is
the @emph{only} way to remove files from @file{/gnu/store}---removing
files or directories manually may break it beyond repair!
+@cindex GC roots
+@cindex garbage collector roots
The garbage collector has a set of known @dfn{roots}: any file under
@file{/gnu/store} reachable from a root is considered @dfn{live} and
cannot be deleted; any other file is considered @dfn{dead} and may be
-deleted. The set of garbage collector roots includes default user
-profiles, and may be augmented with @command{guix build --root}, for
-example (@pxref{Invoking guix build}).
+deleted. The set of garbage collector roots (``GC roots'' for short)
+includes default user profiles; by default, the symlinks under
+@file{/var/guix/gcroots} represent these GC roots. New GC roots can be
+added with @command{guix build --root}, for example (@pxref{Invoking
+guix build}).
Prior to running @code{guix gc --collect-garbage} to make space, it is
often useful to remove old generations from user profiles; that way, old
@@ -5535,9 +5542,17 @@ packages.
@item --root=@var{file}
@itemx -r @var{file}
+@cindex GC roots, adding
+@cindex garbage collector roots, adding
Make @var{file} a symlink to the result, and register it as a garbage
collector root.
+Consequently, the results of this @command{guix build} invocation are
+protected from garbage collection until @var{file} is removed. When
+that option is omitted, build results are eligible for garbage
+collection as soon as the build completes. @xref{Invoking guix gc}, for
+more on GC roots.
+
@item --log-file
Return the build log file names or URLs for the given
@var{package-or-derivation}, or raise an error if build logs are
@@ -6902,7 +6917,8 @@ collection, to make it ``persistent''.
When this option is omitted, the environment is protected from garbage
collection only for the duration of the @command{guix environment}
session. This means that next time you recreate the same environment,
-you could have to rebuild or re-download packages.
+you could have to rebuild or re-download packages. @xref{Invoking guix
+gc}, for more on GC roots.
@item --expression=@var{expr}
@itemx -e @var{expr}