Long story short, I'm using obnam to take backups of my system.

This is what I do:

1. take LVM snapshot of /, /usr, /boot, /var, /home



2. mount the snapshots on /bck-snapshots, /bck-snapshots/usr, /bck-snapshots/boot, /bck-snapshots/var, /bck-snapshots/home




3. run the backup of snapshots:

   
   
   

   obnam backup 
   
       /bck-snapshots 
   
       /bck-snapshots/usr  
   
       /bck-snapshots/boot 
   
       /bck-snapshots/var  
   
       /bck-snapshots/home 
   
   




4. once the backup finishes, umount snapshot filesystems mounted in step 2.




5. remove the snapshots

Problem

during the backup, a system update was done, with a new kernel installed and all the grub2 update dance. Now when I try to remove the root snapshot (step 5.) I get this:

device-mapper: remove ioctl on failed: Device or resource busy

because the snapshot root device is busy and used by another process:

$ sudo lsof /dev/dm-6 # This is the root snapshot device.

lsof: WARNING: can't stat() fuse.gvfsd-fuse file system /run/user/1000/gvfs

      Output information may be incomplete.

COMMAND    PID USER   FD   TYPE DEVICE   SIZE/OFF    NODE NAME

grub-moun 9160 root    3r   BLK  252,6 0t36339712 5295479 /dev/dm-6

Questions

1. I guess that to lvremove the snapshot I have to stop grub-mount to use the device. How to do that safely?




2. I think that the backup snapshot has been added to grub as a viable option to show in the grub menu shown at boot time. What if I remove the corresponding snapshot?




3. Any way to prevent grub from adding the root snapshot found on /bck-snapshots ?

I have to reboot the system in order for the updates to be active, but first I have to know the answer to these questions.