rotate_backup.sh

#!/bin/bash

# for use with cron, eg:
# 0 3 * * * root /home/www/batch/bin/backup.sh /var/backup/www

if [[ -z "$1" ]]; then
    echo "Usage: $0 <PATH>"
    exit 1
fi

TARGET_PATH="$1"; shift
DIR="/var/backup/archives/web"

KEEP_DAILY=7
KEEP_WEEKLY=5
KEEP_MONTHLY=12

if [ -f $TARGET_PATH ] || [ -d $TARGET_PATH ]; then
    TARGET=`basename $TARGET_PATH`
else
	TARGET=$TARGET_PATH
fi

function rotate {
    rotation=$1
    fdate=`date +%Y-%m-%d -d $date`
    file=$DIR/daily/*$fdate*.tar.bz2
    mkdir -p $DIR/$rotation/ || abort
    if [ -f $file ]; then
        cp $file $DIR/$rotation/ || abort
    else
        echo
    fi
}

function prune {  
    dir=$DIR/$1
    keep=$2
	target=$3
    ls $dir | sort -rn | grep -s " ${target}_" | awk " NR > $keep" | while read f; do rm $dir/$f; done
}

function md5_diff {
    dir=$DIR/$1
	target=$2
	date_new=$3
	date_old=$4
	if [ ! -f $dir/${target}_${date_old}.tar.bz2 ]; then
		return 1
	fi
    last=`md5sum $dir/${target}_${date_old}.tar.bz2 | awk '{print $1}'`
	curr=`md5sum $dir/${target}_${date_new}.tar.bz2 | awk '{print $1}'`
	if [ "$last" = "$curr" ]; then
		rm $dir/${target}_${date_new}.tar.bz2
	fi
}

function abort {
    echo "aborting..."
    exit 1
}

mkdir -p $DIR/daily || abort
mkdir -p $DIR/weekly || abort
mkdir -p $DIR/monthly || abort
mkdir -p $DIR/yearly || abort

date=`date +%Y-%m-%d` || abort
day=`date -d $date +%d` || abort
weekday=`date -d $date +%w` || abort
month=`date -d $date +%m` || abort
yesterday=`date -d yesterday +%Y-%m-%d` || abort

# Do the daily backup
oldpath=`pwd`
cd `dirname $TARGET_PATH`
tar jcf $DIR/daily/${TARGET}_${date}.tar.bz2 `basename $TARGET_PATH`
test ${PIPESTATUS[0]} -eq 0 || abort
cd $oldpath ; unset $oldpath

# Perform rotations
if [[ "$weekday" == "0" ]]; then
    rotate weekly
fi
if [[ "$day" == "01" ]]; then
    rotate monthly
fi
if [[ "$month/$day" == "01/01" ]]; then
    rotate yearly
fi

md5_diff daily $TARGET $date $yesterday

prune daily $KEEP_DAILY $TARGET
prune weekly $KEEP_WEEKLY $TARGET
prune monthly $KEEP_MONTHLY $TARGET