I'm using snapper with BTRFS under Ubuntu 16.04, and I'm confused about the "mount" and "umount" parameters. They are documented like this in the man page:

   mount number
       Mount a snapshot. Not required for all filesystem types.

   umount number
       Unmount a snapshot. Not required for all filesystem types.

But where are the snapshots mounted? Does snapper read my mind to know, or just makes an educated guess?

I know how to mount the snapshots using "mount" and the subvol ID, but I would like to know if these "mount" and "umount" options are just a joke or something you can actually use.

Thanks in advance.

  • Oddly enough these are in snapper --help but not in man snapper
    – Warren P
    Jul 14 '16 at 10:50

snapper mount and snapper umount are really only useful when snapper is used with thin-provisioned LVM snapshots. Theese commands will mount and unmount LVM snapshots in the .snapshots/$number/snapshot directory.

Since btrfs subvolumes are always accessible form the .snapshots directory without having to be mounted, snapper mount and snapper umount don't do anything with btrfs.

  • I hadn't seen your reply until now, sorry. I'm marking it as the correct answer. Thanks!
    – rsuarez
    Jul 7 '19 at 10:15

The snapshots are located in a directory called .snapshots in the subvolume. There is a directory corresponding to each snapshot number. I personally can't figure out what mount and umount do. I was unable to find any more information on it than you did.

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