Options in backing up persistent docker volumes?

Use bind mounts instead of docker volumes. Then you just have normal directories to back up, the same as you would anything else.

In general, it's not a problem to back up files while the container is running. The exception to this is databases. To have reliable database backups, you need to stop the container (or quiesce/pause the database if it supports it) before backing up the raw database files (including SQLite).

Rsync works fine for most data. (I use borgbackup) For any database data, create a dump using pg_dump or mysqldump or whatever. Then backup the dump and all other volumes but exclude the db volume.

There is some offical documentation on this: https://docs.docker.com/storage/volumes/#back-up-restore-or-migrate-data-volumes

I personally just rsync my volumes to backblaze :)

My persistent volumes are in a ZFS dataset, and I use Sanoid to periodically snapshot the dataset and Syncoid to transfer these snapshots to my backup host.

In general there is no problem in rsync'ing the volume bind directory. But that depends on the application, which is running in the container. I. e. you should not copy the files of a running database. It may corrupt the data while it's being written.

I personally use a script which stops all containers, rsyncs the bind mounts (normal folders on the filesystem) and then restarts them. It runs every night so it isn't a problem that services are down for a few minutes.

Ideally, you would also make a database dump instead of just backing up the bind mounts.

I have a script that reads all my compose files to determine each container's persistent data (though this could also be done with docker inspect) and then uses docker cp to pipe it into restic, which can use data from stdin.

docker cp mycontainer:/files - | restick backup --stdin --stdin-filename mycontainer

Stopping databases is on my todo list.

Besides using bind mounts(As @[email protected]) mentions, you can run a backup container, that mounts the volume, that you would like to create a backup for. The backup container would handle backing up the volume at regular interval.

This is what I do in thedocker-compose and k3s containers I backup. I can recommend autorestic as the container for backup, but there is a lot of options.

You can copy data from docker volumes to somewhere on the host node to do the backup from there. You can also have a container using the volumes and from there you can send directly to remote, or map a dorectory on the host node to copy the files to.

If you are running a database or something stateful, look at best practices for backup and then adjust to it.

Or not use volumes and map onto the host node directly. each works, and had its own advantages/disadvantages.

Bind mounts are easy to maintain and backup. However if you share data amongst multiple container docker volumes are recommend especially for managing state.

Backup volumes:

docker run --rm --volumes-from dbstore -v $(pwd):/backup containername tar cvf /backup/backup.tar /dbdata

• Launch a new container and mount the volume from the dbstore container
• Mount a local host directory as /backup
• Pass a command that tars the contents of the dbdata volume to a backup.tar file inside /backup directory.

docker docs - volumes

Database volume backup without stopping the service: bash into the container, dump it, and copy it out with docker cp. Run it periodically via crontab