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by merb 49 days ago
How do I backup docker volumes? I never found a native flow for backing up docker compose projects.

While not built in k8s has at least velero and kasten. However they are only possible because of snapshots https://kubernetes.io/docs/concepts/storage/volume-snapshots... and kasten has a plugin like architecture (because of k8s ) that supports application specific backups. However I never found something like that for compose. And that is troublesome in bigger projects like sentry
2 comments
c0balt 49 days ago
The "easiest" way is to use bind mounts to a local directory (or multiple directories) instead of volumes. Then you can just use normal backup tooling.

Docker volumes (and bind mounts) however have the minor problem of being hard to get a consistent copy to without stopping the service. You can work around this by, e. G., having ZFS or btrfs as the underlying FS and making a snapshot there. Otherwise, your software (like PostgreSQL) might also have other online backup tooling.

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mrighele 49 days ago
AFAIK volumes are nothing more than a bind mount on a private docker folder, e.g. the files for volume my-volume are stored in /var/lib/docker/volumes/my-volume/_data, so backup strategies (an problems) for bind mounts apply also to volumes
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c0balt 49 days ago
Yep, that is accurate. There is also a command/API route to find the path on disk iirc.

In my setups it just was easier to use fixed paths (or relative to project dir) from a permissions management perspective. Backup tools did not always have to/should run as root which is helpful on machines providing multiple distinct services.

Putting borg or a similar tool in a container that is part of the compose manifest file can also help. I haven't seen this used in practice though yet.

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mikestorrent 49 days ago
Why use a docker volume? Seems like a good way to accidentally lose your files. Just volume-mount from the external filesystem and back it up the same way you would any linux application's files - maybe stop it, maybe not, depends on how it uses files.
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limaho 49 days ago
Docker volumes still exist on the filesystem. Wouldn't one be able to point the backup solution at that directory?
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mikestorrent 49 days ago
It's nice to be able to survive someone purging Docker by accident, and it's nice to know `/wherever/you/like` is where your files are instead of in `/var/lib/containers/some long hash/`
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