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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | AGGRESSIVE | CONFIGURATION | NOTES | HOOKS | SEE ALSO | GIT | COLOPHON |
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GIT-GC(1) Git Manual GIT-GC(1)
git-gc - Cleanup unnecessary files and optimize the local
repository
git gc [--aggressive] [--auto] [--[no-]detach] [--quiet] [--prune=<date> | --no-prune] [--force] [--keep-largest-pack]
Runs a number of housekeeping tasks within the current repository,
such as compressing file revisions (to reduce disk space and
increase performance), removing unreachable objects which may have
been created from prior invocations of git add, packing refs,
pruning reflog, rerere metadata or stale working trees. May also
update ancillary indexes such as the commit-graph.
When common porcelain operations that create objects are run, they
will check whether the repository has grown substantially since
the last maintenance, and if so run git gc automatically. See
gc.auto below for how to disable this behavior.
Running git gc manually should only be needed when adding objects
to a repository without regularly running such porcelain commands,
to do a one-off repository optimization, or e.g. to clean up a
suboptimal mass-import. See the "PACKFILE OPTIMIZATION" section in
git-fast-import(1) for more details on the import case.
--aggressive
Usually git gc runs very quickly while providing good disk
space utilization and performance. This option will cause git
gc to more aggressively optimize the repository at the expense
of taking much more time. The effects of this optimization are
mostly persistent. See the "AGGRESSIVE" section below for
details.
--auto
With this option, git gc checks whether any housekeeping is
required; if not, it exits without performing any work.
See the gc.auto option in the "CONFIGURATION" section below
for how this heuristic works.
Once housekeeping is triggered by exceeding the limits of
configuration options such as gc.auto and gc.autoPackLimit,
all other housekeeping tasks (e.g. rerere, working trees,
reflog...) will be performed as well.
--[no-]detach
Run in the background if the system supports it. This option
overrides the gc.autoDetach config.
--[no-]cruft
When expiring unreachable objects, pack them separately into a
cruft pack instead of storing them as loose objects. --cruft
is on by default.
--max-cruft-size=<n>
When packing unreachable objects into a cruft pack, limit the
size of new cruft packs to be at most <n> bytes. Overrides any
value specified via the gc.maxCruftSize configuration. See the
--max-cruft-size option of git-repack(1) for more.
--expire-to=<dir>
When packing unreachable objects into a cruft pack, write a
cruft pack containing pruned objects (if any) to the directory
<dir>. This option only has an effect when used together with
--cruft. See the --expire-to option of git-repack(1) for more
information.
--prune=<date>
Prune loose objects older than date (default is 2 weeks ago,
overridable by the config variable gc.pruneExpire).
--prune=now prunes loose objects regardless of their age and
increases the risk of corruption if another process is writing
to the repository concurrently; see "NOTES" below. --prune is
on by default.
--no-prune
Do not prune any loose objects.
--quiet
Suppress all progress reports.
--force
Force git gc to run even if there may be another git gc
instance running on this repository.
--keep-largest-pack
All packs except the largest non-cruft pack, any packs marked
with a .keep file, and any cruft pack(s) are consolidated into
a single pack. When this option is used, gc.bigPackThreshold
is ignored.
When the --aggressive option is supplied, git-repack(1) will be
invoked with the -f flag, which in turn will pass --no-reuse-delta
to git-pack-objects(1). This will throw away any existing deltas
and re-compute them, at the expense of spending much more time on
the repacking.
The effects of this are mostly persistent, e.g. when packs and
loose objects are coalesced into one another pack the existing
deltas in that pack might get re-used, but there are also various
cases where we might pick a sub-optimal delta from a newer pack
instead.
Furthermore, supplying --aggressive will tweak the --depth and
--window options passed to git-repack(1). See the
gc.aggressiveDepth and gc.aggressiveWindow settings below. By
using a larger window size we’re more likely to find more optimal
deltas.
It’s probably not worth it to use this option on a given
repository without running tailored performance benchmarks on it.
It takes a lot more time, and the resulting space/delta
optimization may or may not be worth it. Not using this at all is
the right trade-off for most users and their repositories.
Everything below this line in this section is selectively included
from the git-config(1) documentation. The content is the same as
what’s found there:
gc.aggressiveDepth
The depth parameter used in the delta compression algorithm
used by git gc --aggressive. This defaults to 50, which is the
default for the --depth option when --aggressive isn’t in use.
See the documentation for the --depth option in git-repack(1)
for more details.
gc.aggressiveWindow
The window size parameter used in the delta compression
algorithm used by git gc --aggressive. This defaults to 250,
which is a much more aggressive window size than the default
--window of 10.
See the documentation for the --window option in git-repack(1)
for more details.
gc.auto
When there are approximately more than this many loose objects
in the repository, git gc --auto will pack them. Some
Porcelain commands use this command to perform a light-weight
garbage collection from time to time. The default value is
6700.
Setting this to 0 disables not only automatic packing based on
the number of loose objects, but also any other heuristic git
gc --auto will otherwise use to determine if there’s work to
do, such as gc.autoPackLimit.
gc.autoPackLimit
When there are more than this many packs that are not marked
with *.keep file in the repository, git gc --auto consolidates
them into one larger pack. The default value is 50. Setting
this to 0 disables it. Setting gc.auto to 0 will also disable
this.
See the gc.bigPackThreshold configuration variable below. When
in use, it’ll affect how the auto pack limit works.
gc.autoDetach
Make git gc --auto return immediately and run in the
background if the system supports it. Default is true. This
config variable acts as a fallback in case
maintenance.autoDetach is not set.
gc.bigPackThreshold
If non-zero, all non-cruft packs larger than this limit are
kept when git gc is run. This is very similar to
--keep-largest-pack except that all non-cruft packs that meet
the threshold are kept, not just the largest pack. Defaults to
zero. Common unit suffixes of k, m, or g are supported.
Note that if the number of kept packs is more than
gc.autoPackLimit, this configuration variable is ignored, all
packs except the base pack will be repacked. After this the
number of packs should go below gc.autoPackLimit and
gc.bigPackThreshold should be respected again.
If the amount of memory estimated for git repack to run
smoothly is not available and gc.bigPackThreshold is not set,
the largest pack will also be excluded (this is the equivalent
of running git gc with --keep-largest-pack).
gc.writeCommitGraph
If true, then gc will rewrite the commit-graph file when
git-gc(1) is run. When using git gc --auto the commit-graph
will be updated if housekeeping is required. Default is true.
See git-commit-graph(1) for details.
gc.logExpiry
If the file gc.log exists, then git gc --auto will print its
content and exit with status zero instead of running unless
that file is more than gc.logExpiry old. Default is "1.day".
See gc.pruneExpire for more ways to specify its value.
gc.packRefs
Running git pack-refs in a repository renders it unclonable by
Git versions prior to 1.5.1.2 over dumb transports such as
HTTP. This variable determines whether git gc runs git
pack-refs. This can be set to notbare to enable it within all
non-bare repos or it can be set to a boolean value. The
default is true.
gc.cruftPacks
Store unreachable objects in a cruft pack (see git-repack(1))
instead of as loose objects. The default is true.
gc.maxCruftSize
Limit the size of new cruft packs when repacking. When
specified in addition to --max-cruft-size, the command line
option takes priority. See the --max-cruft-size option of
git-repack(1).
gc.pruneExpire
When git gc is run, it will call prune --expire 2.weeks.ago
(and repack --cruft --cruft-expiration 2.weeks.ago if using
cruft packs via gc.cruftPacks or --cruft). Override the grace
period with this config variable. The value "now" may be used
to disable this grace period and always prune unreachable
objects immediately, or "never" may be used to suppress
pruning. This feature helps prevent corruption when git gc
runs concurrently with another process writing to the
repository; see the "NOTES" section of git-gc(1).
gc.worktreePruneExpire
When git gc is run, it calls git worktree prune --expire
3.months.ago. This config variable can be used to set a
different grace period. The value "now" may be used to disable
the grace period and prune $GIT_DIR/worktrees immediately, or
"never" may be used to suppress pruning.
gc.reflogExpire, gc.<pattern>.reflogExpire
git reflog expire removes reflog entries older than this time;
defaults to 90 days. The value "now" expires all entries
immediately, and "never" suppresses expiration altogether.
With "<pattern>" (e.g. "refs/stash") in the middle the setting
applies only to the refs that match the <pattern>.
gc.reflogExpireUnreachable, gc.<pattern>.reflogExpireUnreachable
git reflog expire removes reflog entries older than this time
and are not reachable from the current tip; defaults to 30
days. The value "now" expires all entries immediately, and
"never" suppresses expiration altogether. With "<pattern>"
(e.g. "refs/stash") in the middle, the setting applies only to
the refs that match the <pattern>.
These types of entries are generally created as a result of
using git commit --amend or git rebase and are the commits
prior to the amend or rebase occurring. Since these changes
are not part of the current project most users will want to
expire them sooner, which is why the default is more
aggressive than gc.reflogExpire.
gc.recentObjectsHook
When considering whether or not to remove an object (either
when generating a cruft pack or storing unreachable objects as
loose), use the shell to execute the specified command(s).
Interpret their output as object IDs which Git will consider
as "recent", regardless of their age. By treating their mtimes
as "now", any objects (and their descendants) mentioned in the
output will be kept regardless of their true age.
Output must contain exactly one hex object ID per line, and
nothing else. Objects which cannot be found in the repository
are ignored. Multiple hooks are supported, but all must exit
successfully, else the operation (either generating a cruft
pack or unpacking unreachable objects) will be halted.
gc.repackFilter
When repacking, use the specified filter to move certain
objects into a separate packfile. See the
--filter=<filter-spec> option of git-repack(1).
gc.repackFilterTo
When repacking and using a filter, see gc.repackFilter, the
specified location will be used to create the packfile
containing the filtered out objects. WARNING: The specified
location should be accessible, using for example the Git
alternates mechanism, otherwise the repo could be considered
corrupt by Git as it might not be able to access the objects
in that packfile. See the --filter-to=<dir> option of
git-repack(1) and the objects/info/alternates section of
gitrepository-layout(5).
gc.rerereResolved
Records of conflicted merge you resolved earlier are kept for
this many days when git rerere gc is run. You can also use
more human-readable "1.month.ago", etc. The default is 60
days. See git-rerere(1).
gc.rerereUnresolved
Records of conflicted merge you have not resolved are kept for
this many days when git rerere gc is run. You can also use
more human-readable "1.month.ago", etc. The default is 15
days. See git-rerere(1).
git gc tries very hard not to delete objects that are referenced
anywhere in your repository. In particular, it will keep not only
objects referenced by your current set of branches and tags, but
also objects referenced by the index, remote-tracking branches,
reflogs (which may reference commits in branches that were later
amended or rewound), and anything else in the refs/* namespace.
Note that a note (of the kind created by git notes) attached to an
object does not contribute in keeping the object alive. If you are
expecting some objects to be deleted and they aren’t, check all of
those locations and decide whether it makes sense in your case to
remove those references.
On the other hand, when git gc runs concurrently with another
process, there is a risk of it deleting an object that the other
process is using but hasn’t created a reference to. This may just
cause the other process to fail or may corrupt the repository if
the other process later adds a reference to the deleted object.
Git has two features that significantly mitigate this problem:
1. Any object with modification time newer than the --prune date
is kept, along with everything reachable from it.
2. Most operations that add an object to the database update the
modification time of the object if it is already present so
that #1 applies.
However, these features fall short of a complete solution, so
users who run commands concurrently have to live with some risk of
corruption (which seems to be low in practice).
The git gc --auto command will run the pre-auto-gc hook. See
githooks(5) for more information.
git-prune(1) git-reflog(1) git-repack(1) git-rerere(1)
Part of the git(1) suite
This page is part of the git (Git distributed version control
system) project. Information about the project can be found at
⟨http://git-scm.com/⟩. If you have a bug report for this manual
page, see ⟨http://git-scm.com/community⟩. This page was obtained
from the project's upstream Git repository
⟨https://github.com/git/git.git⟩ on 2025-08-11. (At that time,
the date of the most recent commit that was found in the
repository was 2025-08-07.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
Git 2.51.0.rc1 2025-08-07 GIT-GC(1)
Pages that refer to this page: git(1), git-config(1), git-fast-import(1), git-fetch(1), git-gc(1), git-maintenance(1), git-p4(1), git-pack-objects(1), git-prune(1), git-reflog(1), git-repack(1), gitformat-pack(5), githooks(5), gitrepository-layout(5), gitnamespaces(7)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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