system-wide backup to btrfs with rsync

backupgentoo.sh

#!/bin/sh

PART_LABEL=linuxbackup
DEST_DIR=/mnt/backup
snapshot_name=`date +bak_%Y%m%d`

echo "Before running this script, please make sure have your fstab set up."
echo "A working example looks like:"
cat <<EOF
/dev/sdb2            /              <FS>    <MOUNT_OPTS>             0 1
/dev/sdb2            /home          <FS>    <MOUNT_OPTS>             0 1
LABEL=linuxbackup    /mnt/backup    btrfs   subvol=latest,noauto,rw  0 0
EOF

echo "pausing for 3 secs, you will have chance to interrupt this script."
seq 3 | while read x; do
    sleep 1
    echo -n '.'
done
echo

echo 'checking if the device is been using'
if [ $(lsof $DEST_DIR | wc -l) != "0" ]; then
    echo 'backup stopped, the device is been used, here output the result of lsof'
    lsof $DEST_DIR
    exit
fi

echo 'mounting backup device'
sync
umount $DEST_DIR
mount $DEST_DIR 2>/dev/null

echo 'rsync-ing root'
rsync --force --progress --delete-excluded -avx / $DEST_DIR \
    --exclude '/tmp/*' \
    --exclude '/var/tmp/*' \
    --exclude '/dev/*' \
    --exclude '/proc/*' \
    --exclude '/sys/*' \
    || exit

echo 'rsync-ing home'
rsync --force --progress --delete-excluded -avx /home/ $DEST_DIR/home \
    --exclude '/home/*/tmp' \
    --exclude '/home/*/.cache' \
    || exit

echo 'generating snapshot'
sync
umount $DEST_DIR || exit
mount -t btrfs -o subvolid=0,rw /dev/disk/by-label/linuxbackup $DEST_DIR || exit
btrfs subvolume delete "$DEST_DIR/$snapshot_name" 2>/dev/null
btrfs subvolume snapshot -r $DEST_DIR/latest $DEST_DIR/$snapshot_name    || exit

echo 'umounting backup device'
sync
umount $DEST_DIR || exit

echo 'done'