#1657 Issue closed: With btrfs 'rear checklayout' always detects a changed layout¶

Labels: enhancement, fixed / solved / done, minor bug

jsmeix opened issue at 2017-12-21 13:35:¶

With btrfs 'rear checklayout' always detects a changed layout

Reason:
A changed layout is detected in
layout/compare/default/500_compare_layout.sh
via

diff -u <(grep -v '^#' $ORIG_LAYOUT) <(grep -v '^#' $TEMP_LAYOUT) >/dev/null

In case of btrfs the ordering of the btrfsmountedsubvol
entries is random so that plain 'diff' detects changes
in var/lib/rear/layout/disklayout.conf
versus /tmp/rear.XXX/tmp/checklayout.conf

The fix is to additionally sort the entries in the layout files:

diff -u <( grep -v '^#' $ORIG_LAYOUT | sort ) <( grep -v '^#' $TEMP_LAYOUT | sort ) >/dev/null

jsmeix commented at 2017-12-21 13:42:¶

I see no reason why 'diff -u' is used
when its output is nowhere consumed.

To plain compare files 'cmp -s' is the right tool,
cf. the various 550_rebuild_initramfs.sh scripts
and 260_recovery_storage_drivers.sh

jsmeix commented at 2017-12-21 14:22:¶

This usr/share/rear/layout/compare/default/500_compare_layout.sh
makes it work for me:

# Test if ORIG_LAYOUT and TEMP_LAYOUT are the same.

# In case of btrfs the ordering of the btrfsmountedsubvol entries is random
# so that plain 'cmp' would detect changes unless the entries were sorted:
if cmp -s <( grep -v '^#' $ORIG_LAYOUT | sort ) <( grep -v '^#' $TEMP_LAYOUT | sort ) ; then
    LogPrint "Disk layout is identical"
else
    # The 'cmp' exit status is 0 if inputs are the same, 1 if different, 2 if trouble.
    # In case of 'trouble' do the same as when the layout has changed to be on the safe side:
    LogPrint "Disk layout has changed"
    # In the log file show the changes in the right ordering in the layout files:
    diff -U0 <( grep -v '^#' $ORIG_LAYOUT ) <( grep -v '^#' $TEMP_LAYOUT ) >&2
    EXIT_CODE=1
fi

---

[Export of Github issue for rear/rear.]