On Sun, Apr 10, 2016 at 03:47:44PM +0100, Richard C wrote: > Hi, > > I'm writing a backup script that images a btrfs using btrfs-image, You are aware that btrfs-image copies only the metadata? The data is _not_ a part of the image, so it's a fairly poor implementation of a backup process. Hugo. > then restores to a file on a loop device. Since I had trouble mounting > the original and copied btrfs filesystems with the same UUID on the > same machine, I decided to try btrfstune -fu. However, this appears to > corrupt the copied filesystem altogether making fsck and mount fail. > Details below. > Is this a bug? > > $ uname -a > Linux adventure 3.16.0-67-generic #87~14.04.1-Ubuntu SMP Fri Mar 11 > 00:26:02 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux > $ btrfs --version > btrfs-progs v4.4 > > $ btrfstune -fu /dev/loop2 > Current fsid: 36012b08-1e33-4d3c-ac23-5ccffd3295cd > New fsid: 8f70d0af-8ffa-4c82-a817-941e6abfaf9a > Set superblock flag CHANGING_FSID > Change fsid in extents > Change fsid on devices > Clear superblock flag CHANGING_FSID > Fsid change finished > > $ btrfs check /dev/loop2 > fsid mismatch, want=36012b08-1e33-4d3c-ac23-5ccffd3295cd, > have=8f70d0af-8ffa-4c82-a817-941e6abfaf9a > Couldn't read chunk root > Couldn't open file system > $ echo $? > 251 > > $ mount /dev/loop2 /mnt > mount: wrong fs type, bad option, bad superblock on /dev/loop2, > missing codepage or helper program, or other error > In some cases useful info is found in syslog - try > dmesg | tail or so > $ echo $? > 32 -- Hugo Mills | There's many a slip 'twixt wicket-keeper and gully. hugo@... carfax.org.uk | http://carfax.org.uk/ | PGP: E2AB1DE4 |
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