Re: Incremental Backup of repositories using Git

["Michal Suchánek" <msuchanek@suse.de>]

On Mon, May 05, 2025 at 02:35:43PM +0000, Akash S wrote:
> Hi,
> 
> Currently we are backing up repositories using the "git clone -bare" command and save it to disk. If we want to restore, we just run git push -mirror from the repo that was saved during the backup.
> 
> Currently we are running full backups (run git clone -bare) everyday, which is taking a lot of disk space and time.
> 
> Are there any possible ways to backup only the incremental changes of a repository? And somehow construct the whole repository when we want to do a restore from the incremental backups?

Hello,

first, to make it easier to update the backup the clone should be done
with --bare --mirror.

If your clone ends up having multiple packs and loose objects you
can reduce its size with

git --git-dir=/path/to/clone repack -adk

This should give you a repository with a single pack and no loose
objects.

The -k (or --cruft) option is required, using only -ad seems to corrupt
repositories quite reliably.

To speed up the clone next time around you can make a copy of the
previous backup and fetch from the remote repository but because
there is no safe way I am aware of to eliminate no longer referenced
objects you will accumulate cruft this way.

This is now a complete backup, and should be made readonly to not get
corrupted with further operations.

The inrementeal backups are somewhat speculative, I have not tested this
at all.

You can create a shared clone of the full backup, update the origin URL
of the shared clone to the remote repository to backup, and do a fetch
-p (which now should do the right thing because the initial clone was
set up as mirror).

To repack you need to use the --local option in addition.

With this you should have a valid repository for each backup with the
incremental backups sharing most objects with the full backup.

These can be inspected with git commands, exported over gitweb, or
whatever.

Thanks

Michal