So it seems that FFS snapshots cannot be used with dump/restore to
recover file system data from a previous snapshot. It fails with device
busy error.
I can fall back to tar instead, however am I correct in thinking that
NetBSD dump/restore are simply not usable in this case?
I've done a similar procedure on FreeBSD and it works correctly, but
I think they may have made specific fixes to dump/restore for
snapshots? I'm not sure.
Access snapshot at /mnt/.snapshots/latest:
# mount -o log NAME=NetBSD-diag /mnt
# snapshot_root="/mnt"
# snapshot_dir="${snapshot_root:?}/.snapshots"
# snapshot_name="${snapshot_dir:?}/latest"
Configure /dev/fss0 snapshot device:
# fssconfig fss0 ${snapshot_root:?} ${snapshot_name:?}
Restore data from /dev/fss0 to the same file system:
# (cd ${snapshot_root:?} && dump -0 -a -h 0 -b 64 -f - /dev/fss0 | restore
-xuvf -)
Verify tape and initialize maps
DUMP: Date of this level 0 dump: Thu Nov 20 09:48:09 2025
DUMP: Date of last level 0 dump: the epoch
DUMP: Dumping /dev/fss0 (an unlisted file system) to standard output
DUMP: Label: none
DUMP: mapping (Pass I) [regular files]
DUMP: mapping (Pass II) [directories]
DUMP: estimated 400044 tape blocks.
DUMP: worker couldn't reopen disk DUMP: Volume 1 started at: Thu Nov 20
09:48:10 2025
DUMP: dumping (Pass III) [directories]
DUMP: worker couldn't reopen disk DUMP: : Device busy
: Device busy
DUMP: The ENTIRE dump is aborted.
End-of-tape encountered
Checksum error 0, inode 0 file <name unknown>
Tape is not a dump tape
