[linux-lvm] Restore LVM snapshot without creating a full dump to an "external" device?

Bas van Schaik bas at tuxes.nl
Sun Mar 9 22:05:45 UTC 2008

Hi all,

When I started to use LVM snapshots, I presumed that it was easy to
restore a system to such a snapshot. As far as I can see now, this
presumption was incorrect... People on the internet write that I should
dump the whole snapshot using dd and then write it over the original
volume. This actually implies that I need another device with at least
the size of the original volume available to dump to. In my situation,
this means that I need about 2 TB free space to recover this snapshot!

Isn't there a more sophisticated way to restore the snapshot than just
dumping it?
 1) create snapshot of /dev/myvolumegroup/myvolume to
 2) dd if=/dev/myvolumegroup/mysnapshot of=/tmp/mysnapshot.dd
 3) lvremove /dev/myvolumegroup/mysnapshot
 4) dd if=/tmp/mysnapshot.dd of=/dev/myvolumegroup/myvolume

Something like:
 1) lvrevert /dev/myvolumegroup/mysnapshot /dev/myvolumegroup/myvolume

I'd like to hear your thoughts on this, because I think it should be
fairly easy to restore a COW snapshot. Or am I wrong and missing something?



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