backup.sh

#!/usr/bin/env bash

VERSION='2.0'
DESC='Rotating incremental backup'

#set -o errtrace
set -o errexit


#-- VARS --#

# Extra rsync options
OPTS='--exclude "lost+found"'


#-- FUNCTIONS --#

# Version & usage info
version() { echo "`basename $0` $VERSION - $DESC"; }
usage() {
  version
  echo "
Usage:
  `basename $0` source destination [rotation]

Arguments:
  source       - The source directory to backup.
  destination  - The destination where to place the backup.
  rotation     - How many backups to rotate. Defaults to 3.
"
}

# Error handling
log()         { $* >> $LOG 2>&1; return $?; }
fail()        { echo "*** ERROR: $* ***"; exit 1; }
fail_usage()  { echo -e "*** ERROR: $* ***\n"; usage; exit 1; }
try()         { log $* || fail "Please check $LOG!"; }


#-- CHECKS --#

# Make sure we're running as root
[[ "`id -u`" == '0' ]] || fail "Please run this script as root!"

# Make sure $SRCDIR exists
[[ -n "$1" ]] && SRCDIR="$1" || {
  fail_usage "Please specify the source to synchronise!"
}
[[ -d "$SRCDIR" ]] || fail "Source $SRCDIR does not exist!"

# Make sure $DESDIR exists
[[ -n "$2" ]] && DESDIR="$2" || {
  fail_usage "Please specify the destination!"
}
[[ -d "$DESDIR" ]] || fail "Destination $DESDIR does not exist!"

# How many backups to rotate
[[ -n "$3" ]] && ROTATE="$3" || ROTATE=3
[[ "$ROTATE" -gt 1 ]] || fail "Rotation must be greater than 1!"

# Set the $TMPDIR
[[ -n "$TMPDIR" ]] || TMPDIR='/tmp'
[[ -d "$TMPDIR" ]] || fail "Temporary dir $TMPDIR does not exist!"

# Name of the logfile
LOG="$TMPDIR/`basename $0`.log"


#-- SCRIPT --#

rm -f $LOG
echo "----------------------- Backup -----------------------"

NAME=`echo "$SRCDIR" | sed 's/\///g'`
NEWESTBAK=`ls -1 $DESDIR | grep backup_$NAME | tail -1`
CURRENTBAK="backup_${NAME}_`date +%Y%m%d%H%M%S`"

# Create hardlinks from $NEWESTBAK to $CURRENTBAK
if [ ! -z $NEWESTBAK ]; then
  echo " > Creating hardlinks..."
  try cp -al $DESDIR/$NEWESTBAK $DESDIR/$CURRENTBAK
fi

# Do the actual synchronisation
echo " > Synchronizing newest data..."
try rsync -a --delete $OPTS $SRCDIR/ $DESDIR/$CURRENTBAK/

# Remove old backups
NUMBAK=`ls -1 $DESDIR | grep -c backup_$NAME`
if [ "$NUMBAK" -gt "$ROTATE" ]; then
  echo " > Removing old backups..."
  NUMREM=$[$NUMBAK-$ROTATE]
  cd $DESDIR
  for BAK in `ls -1 | grep backup_$NAME | head -$NUMREM`; do
    rm -rf $BAK
  done
fi

echo "-----------------------  Done  -----------------------"
rm -f $LOG && exit 0