Packages that are installed, but not used, may be garbage-collected.
guix gc command allows users to explicitly run the garbage
collector to reclaim space from the /gnu/store directory. It is
the only way to remove files from /gnu/store—removing
files or directories manually may break it beyond repair!
The garbage collector has a set of known roots: any file under
/gnu/store reachable from a root is considered live and
cannot be deleted; any other file is considered dead and may be
deleted. The set of garbage collector roots (“GC roots” for short)
includes default user profiles; by default, the symlinks under
/var/guix/gcroots represent these GC roots. New GC roots can be
guix build --root, for example (see Invoking guix build). The
guix gc --list-roots command lists them.
Prior to running
guix gc --collect-garbage to make space, it is
often useful to remove old generations from user profiles; that way, old
package builds referenced by those generations can be reclaimed. This
is achieved by running
guix package --delete-generations
(see Invoking guix package).
Our recommendation is to run a garbage collection periodically, or when you are short on disk space. For instance, to guarantee that at least 5 GB are available on your disk, simply run:
guix gc -F 5G
It is perfectly safe to run as a non-interactive periodic job
(see Scheduled Job Execution, for how to set up such a job).
guix gc with no arguments will collect as
much garbage as it can, but that is often inconvenient: you may find
yourself having to rebuild or re-download software that is “dead” from
the GC viewpoint but that is necessary to build other pieces of
software—e.g., the compiler tool chain.
guix gc command has three modes of operation: it can be
used to garbage-collect any dead files (the default), to delete specific
files (the --delete option), to print garbage-collector
information, or for more advanced queries. The garbage collection
options are as follows:
Collect garbage—i.e., unreachable /gnu/store files and sub-directories. This is the default operation when no option is specified.
When min is given, stop once min bytes have been collected.
min may be a number of bytes, or it may include a unit as a
suffix, such as
MiB for mebibytes and
GB for gigabytes
(see size specifications in GNU Coreutils).
When min is omitted, collect all the garbage.
Collect garbage until free space is available under
/gnu/store, if possible; free denotes storage space, such
500MiB, as described above.
When free or more is already available in /gnu/store, do nothing and exit immediately.
Before starting the garbage collection process, delete all the generations older than duration, for all the user profiles; when run as root, this applies to all the profiles of all the users.
For example, this command deletes all the generations of all your profiles that are older than 2 months (except generations that are current), and then proceeds to free space until at least 10 GiB are available:
guix gc -d 2m -F 10G
Attempt to delete all the store files and directories specified as arguments. This fails if some of the files are not in the store, or if they are still live.
List store items corresponding to cached build failures.
This prints nothing unless the daemon was started with --cache-failures (see --cache-failures).
List the GC roots owned by the user; when run as root, list all the GC roots.
List store items in use by currently running processes. These store items are effectively considered GC roots: they cannot be deleted.
Remove the specified store items from the failed-build cache.
Again, this option only makes sense when the daemon is started with --cache-failures. Otherwise, it does nothing.
Show the list of dead files and directories still present in the store—i.e., files and directories no longer reachable from any root.
Show the list of live store files and directories.
In addition, the references among existing store files can be queried:
List the references (respectively, the referrers) of store files given as arguments.
List the requisites of the store files passed as arguments. Requisites include the store files themselves, their references, and the references of these, recursively. In other words, the returned list is the transitive closure of the store files.
See Invoking guix size, for a tool to profile the size of the closure of an element. See Invoking guix graph, for a tool to visualize the graph of references.
Return the derivation(s) leading to the given store items (see Derivations).
For example, this command:
guix gc --derivers $(guix package -I ^emacs$ | cut -f4)
returns the .drv file(s) leading to the
installed in your profile.
Note that there may be zero matching .drv files, for instance because these files have been garbage-collected. There can also be more than one matching .drv due to fixed-output derivations.
Lastly, the following options allow you to check the integrity of the store and to control disk usage.
Verify the integrity of the store.
By default, make sure that all the store items marked as valid in the database of the daemon actually exist in /gnu/store.
When provided, options must be a comma-separated list containing one
or more of
When passing --verify=contents, the daemon computes the content hash of each store item and compares it against its hash in the database. Hash mismatches are reported as data corruptions. Because it traverses all the files in the store, this command can take a long time, especially on systems with a slow disk drive.
Using --verify=repair or --verify=contents,repair
causes the daemon to try to repair corrupt store items by fetching
substitutes for them (see Substitutes). Because repairing is not
atomic, and thus potentially dangerous, it is available only to the
system administrator. A lightweight alternative, when you know exactly
which items in the store are corrupt, is
guix build --repair
(see Invoking guix build).
Optimize the store by hard-linking identical files—this is deduplication.
The daemon performs deduplication after each successful build or archive import, unless it was started with --disable-deduplication (see --disable-deduplication). Thus, this option is primarily useful when the daemon was running with --disable-deduplication.