On an btrfs volume, I have a folder
snapshots/ in which I store a snapshot of the whole volume from time to time.
btrfs automatically mounts all subvolumes, eg. after mounting the top volume,
snapshots/ is populated with all snapshots ever done.
Now I like to unmount the subvolumes in
snapshots empty (without deleting the snapshots of course). This is very useful if I do backups, indexing or searching on the volume, which otherwise always needs to be limited in a tool-dependent fashion to exclude
snapshots/, which is not always easy.
As the subvolumes are not mounted by kernel, I cannot unmount them with
mount. How to unmount them?