I cannot delete a the btrfs subvolume "2014-07-28" which is a snapshot of the "@" created by the kubuntu installer to serve as the kubuntu root.
teneighty@teneighty-MS-7924:/$ sudo mount -o subvolid=5 /dev/sda5 /mnt teneighty@teneighty-MS-7924:/$ sudo btrfs sub list /mnt ID 257 gen 1782 top level 5 path @ ID 258 gen 1574 top level 5 path @home ID 266 gen 1761 top level 5 path 2014-07-28 teneighty@teneighty-MS-7924:/$ ls /mnt @ 2014-07-28 @home teneighty@teneighty-MS-7924:/$ sudo btrfs sub del /mnt/2014-07-28/ Delete subvolume '/mnt/2014-07-28' ERROR: cannot delete '/mnt/2014-07-28' - Operation not permitted
tried apt-btrfs-snapshot delete:
teneighty@teneighty-MS-7924:/$ sudo apt-btrfs-snapshot delete /mnt/2014-07-28/ Delete subvolume '/mnt/2014-07-28' ERROR: cannot delete '/mnt/2014-07-28' - Device or resource busy
if it's busy, I shouldn't be able to do this, should I?
teneighty@teneighty-MS-7924:/$ sudo umount /mnt
but it unmounts quietly. Although I tested and it will unmount even if I have /mnt/2014-07-28 open in a file manager.
I created the snapshot after installing kubuntu 14.04, and then performed a substantial system update. After the update I created another snapshot, and I was able to delete that one without a problem. But the one I want to delete is the preupdate snapshot since everything is working fine post-update, I don't expect I will need to roll back to a fresh installion stage.
I have also attempted to delete it using the kubuntu live USB I installed from, that didn't work either. Then I tried apt-btrfs-snapshot delete, and
It is likely that this snapshot was originally located at @/snapshots/2014-07-28, and then I gained a better understanding of the ubuntu BTRFS layout from documentation at help.ubuntu.com, so I moved my snapshots to the root BTRFS volume. I tried to move it back, but it returned the same error.
What could be causing this error on a snapshot? Why would apt-btrfs-snapshot say it is busy? I don't know where to go from here, but as the file system changes, I am going to need that space back.