backup rsync

bkp_snapshot.sh

#!/bin/bash

# reference
# http://www.mikerubel.org/computers/rsync_snapshots/#Extensions

# CRON
# 0 */4 * * * /usr/local/bin/bkp_snapshot.sh >/dev/null 2>&1

unset PATH

# ------------- system commands used by this script --------------------

ECHO=/bin/echo
RM=/bin/rm
MV=/bin/mv
CP=/bin/cp
TOUCH=/bin/touch
RSYNC=/usr/bin/rsync

# ------------- file locations -----------------------------------------
BACKUPDIR=/bkp

# ------------- the script itself --------------------------------------

# step 1: delete the oldest snapshot, if it exists:
if [ -d $BACKUPDIR/home/hourly.3 ] ; then
    $ECHO "oldest snapshot founded. Deleting!"
    $RM -rf $BACKUPDIR/home/hourly.3
fi

# step 2: shift the middle snapshots(s) back by one, if they exist
if [ -d $BACKUPDIR/home/hourly.2 ] ; then
    $MV $BACKUPDIR/home/hourly.2 $BACKUPDIR/home/hourly.3
fi

if [ -d $BACKUPDIR/home/hourly.1 ] ; then
    $MV $BACKUPDIR/home/hourly.1 $BACKUPDIR/home/hourly.2
fi

# step 3: make a hard-link-only (except for dirs) copy of the latest snapshot
if [ -d $BACKUPDIR/home/hourly.0 ] ; then
    $CP -al $BACKUPDIR/home/hourly.0 $BACKUPDIR/home/hourly.1
fi

# step 4: rsync from the system into the latest snapshot (notice that
# rsync behaves like cp --remove-destination by default, so the destination
# is unlinked first.  If it were not so, this would copy over the other
# snapshot(s) too!
$RSYNC                          \
    -va --delete                \
    /home/ $BACKUPDIR/home/hourly.0

# step 5: update the mtime of hourly.0 to reflect the snapshot time
$TOUCH $BACKUPDIR/home/hourly.0