Allow snapshots of container volumes

[darkdragon-001]

Feature request description

It would be great of there was a way to snapshot and restore container volumes.

Suggest potential solution

If containers/storage drivers (like btrfs) would also be used for container volumes in addition to container image layers, then snapshots of volumes would almost come for free, as there is already functionality to commit the current writable layer.

Have you considered any alternatives?

Manually copying the files.

Additional context

This could be used as backup to restore in case anything goes wrong.

[Luap99]

also see #10665

I don't think the opinion has changed since. You can still snapshot the volumes externally without podman.

[darkdragon-001]

@Luap99 no it's not possible to snapshot them individually as they are not separate subvolumes but only folders. Using the storage driver would provide all this functionality for free. Also one would not need to create two different things for layers and volumes but would only need to write a single plugin which can be used for both (or reuse the big ecosystem of existing ones).

[Luap99]

There is no such thing as "for free", code needs to be written, maintained, tested, etc... The btrfs driver is already basically unmaintained to my knowledge and most people use overlayfs anyway so this feature would have no benefit to them.

I doubt that any of the current maintainers would be interested in working on this, if someone else is willing to step up and and do the work AND maintain it then we are generally open to contributions.

[darkdragon-001]

"for free" as one only needs to adapt the interface and can then use all available implementations.

Even when using the overlayfs driver, one could "commit" a layer which basically creates a snapshot.

[rhatdan]

Volumes support a plugin interface someone, would need to implement a btrfs or other snapshotting mechanism. No such tool that I know of does now. Volumes are not using containers/storage now, that I know of.

[IBims1NicerTobi]

Can you kindly link the documentation for the plugin interface? I look and did not find anything.