[SOLVED] How to mount an LXC snapshot? [device /dev/vg/snap does not exist]

[moxfan]

Hi Guys,

Is it even possible to mount an LXC snapshot?

root@prox1:~# lvcreate -s --name snap vg/vm-100-disk-0
  Logical volume "snap" created.

root@prox1:~# lvs
  LV            VG  Attr       LSize   Pool Origin        Data%  Meta%  Move Log Cpy%Sync Convert
  cts           vg twi-aotz--   1.68t                    1.25   0.23
  snap          vg Vwi---tz-k 100.00g cts  vm-100-disk-0
  vm-100-disk-0 vg Vwi-aotz-- 100.00g cts                21.55

root@prox1:~# mkdir snapmount

root@prox1:~# mount /dev/vg/snap snapmount
mount: /root/snapmount: special device /dev/vg/snap does not exist.

root@prox1:~# mount /dev/mapper/vg-snap snapmount
mount: /root/snapmount: special device /dev/mapper/vg-snap does not exist.

 

[dcsapak]

you probably have to activate the snapshot with lvchange first before udev creates the /dev/mapper or /dev/vg links

 

[moxfan]

you probably have to activate the snapshot with lvchange first before udev creates the /dev/mapper or /dev/vg links

Thanks for giving me the clue.

This didn't work:

lvchange -ay vg/snap

This worked and prepared the snapshot for mounting:

lvchange -ay -Ky vg/snap

From "man lvchange" :

-K|--ignoreactivationskip
              Ignore the "activation skip" LV flag during activation to allow LVs with the flag set
              to be activated.

A re-writeable snapshot mount was ready in less than 1 minute (a 20GB container). A read-only mount was instantly available, as expected.