Many thanks to Rich, Miles, Vitor and Laurence for their hints on this
subject.
Especially the suggestion to use BTRFS Snapshots was very helpful.
Finally I have come up with the following shell script for backing up
my /home directory,
comments are more than welcome, of course.
(/HBackUp contains a BTRFS file system)
#!/bin/zsh
mount /HBackUp
pushd /HBackUp
NUM_TO_KEEP=5
if [ -d "ohome_$NUM_TO_KEEP" ]
then
btrfs subvolume delete "ohome_$NUM_TO_KEEP"
fi
if ! [ -f _RSync_Failed ]
then
for backup_no in $(seq $((NUM_TO_KEEP-1)) -1 1)
do
if [ -d ohome_$backup_no ]
then
backup_no_plus_1="$((backup_no+1))"
mv $ohome_prev "ohome_$backup_no_plus_1"
fi
done
if ! btrfs subvolume snapshot ohome ohome_1
then
echo Sorry, creating snapshot ohome_1 failed 1>&2
exit 1
fi
fi
RSync_OK=False
touch _RSync_Failed
popd
pushd /home
if rsync -aqxAHSW --delete . /HBackUp/ohome/
then
RSync_OK=True
else
case "$?" in
23)
# This means some files gave permission denied - assume
that's OK
RSync_OK=True
;;
24)
# This means one or more files disappeared
RSync_OK=True
;;
*)
echo rsync failed. Exit code was $?"
;;
esac
fi
popd
cd /HBackUp
case "$RSync_OK" in
True)
rm _RSync_Failed
;;
False)
cd /
umount /HBackUp
exit 1
;;
esac
cd /
umount /HBackUp
