On Thu, Dec 01, 2011 at 09:44:53PM -0600, Douglas McClendon wrote: > The commandline to do the 'edit' was requested for users like Fred, and > because I guess one day I might find myself wanting to do the same. This is unsupported, but if you want to try: You need to flip the 5th byte of the 'cow' device from 0 to 1 (when the snapshot is not active). (But you might have lost the most recent changes if they weren't flushed out when it filled up.) Something like this: # lvs LV VG Attr LSize Origin Snap% Move Log Copy% Convert lvol0 vg2 owi-a- 10.00m lvol1 vg2 Swi-I- 10.00m lvol0 100.00 # dmsetup table vg2-lvol1-cow 0 20480 linear 7:0 22528 # lvchange -an vg2/lvol0 # dmsetup create tmp-vg2-lvol1-cow --table "0 20480 linear 7:0 22528" # hexdump -C /dev/mapper/tmp-vg2-lvol1-cow | head -1 00000000 53 6e 41 70 00 00 00 00 01 00 00 00 08 00 00 00 |SnAp............| Flip byte 5, e.g. copy to file, edit that bit, copy back. # dd if=/dev/mapper/tmp-vg2-lvol1-cow of=/tmp/cow-start bs=512 count=1 # vim -b /tmp/cow-start (and/or xxd) # dd if=/tmp/cow-start of=/dev/mapper/tmp-vg2-lvol1-cow # dmsetup remove tmp-vg2-lvol1-cow # lvchange -ay vg2/lvol0 # lvs LV VG Attr LSize Origin Snap% Move Log Copy% Convert lvol0 vg2 owi-a- 10.00m lvol1 vg2 swi-a- 10.00m lvol0 10.08 # hexdump -C /dev/mapper/vg2-lvol1-cow | head -1 00000000 53 6e 41 70 01 00 00 00 01 00 00 00 08 00 00 00 |SnAp............| Alasdair -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
