This is a pair of scripts i designed in order to create and restore easily incremental backups of a game server, they allow you to backup automatically a specific folder every 30 minutes every backup is labeled with date hour/minutes/seconds and the script flush every backups that are older than seven days (you can change that obviously)

The system uses incremental updates through the “dar” program, it creates a master backup file every mornings at 0:00 and creates incremental backups every 30 minutes. This means only what changed through the day is saved instead of having one full backup 48 times a day.

this script you should execute through a cron job:

#/bin/sh
#script: backup_incremental.sh
#the folder we want to backup is /home/username/folder_to_backup

WORKING_DIR=/home/username
FOLDER=folder_to_backup
BACKUP_FOLDER=/my/BACKUP

DAY=`date -I`
HOUR=`date +%H%M%S`

#this define the day date of the backups we want to delete
OLD=`date -I -d "-1weeks"`

cd $WORKING_DIR

if [ -f ${BACKUP_FOLDER}/${DAY}.1.dar ]
then
	echo "master backup exist, making incremental update."
	LASTSLICE=`ls -1cr ${BACKUP_FOLDER}/${DAY}*.dar |tail -1`
	echo "last slice is: ${LASTSLICE}"
	dar -c ${BACKUP_FOLDER}/${DAY}-${HOUR} -R ${WORKING_DIR}/${FOLDER} -P . -A ${LASTSLICE%%.*}
else
	echo "creating daily master backup"
	dar -c ${BACKUP_FOLDER}/${DAY} -R ${WORKING_DIR}/${FOLDER} -P .
	echo "deleting 7 days old backup (${OLD})"

	#we remove the older backups, if we can
	rm ${BACKUP_FOLDER}/${OLD}*
fi

Example cron job to execute this script (dev/null is required because dar tend to be quite chatty):

*/30 * * * * /home/user/scripts/backup_incremental.sh >> /dev/null 2>&1

Restoring backups with dar is a little tedious because you have to restore every incremental backups one by one. This script will restore the master backup and every incremental backups up to the one you defined in the folder of your choice.

#/bin/sh
#script: restore_incremental.sh

if [ -n "$3" ]; then
        if [ -f "$1" ]; then
                if [ -f "$2" ]; then

                        FS_ROOT="$3"
                        MASTER_DAR="${1%%.*}"
                        LAST_BACKUP="${2%%.*}"
                        FILES=`ls -m1cr ${MASTER_DAR}*.dar`

                        echo "MASTER DAR FILE is: ${MASTER_DAR}"
                        echo "LAST BACKUP is: ${LAST_BACKUP}"
                        echo "File list: ${FILES}"

                        for file in ${FILES}; do
                                echo "Processing... ${file}"
                                dar -Ox ${file%%.*} -w -R "$FS_ROOT"
                                if [ "${file%%.*}" == "${LAST_BACKUP}" ]; then
                                        echo "This was our last file."
                                        break
                                fi
                        done
                        echo "All done."
                else
                        echo "ERROR: this increment doesn't exist."
                fi
        else
                echo "ERROR: this base dar doesn't exist."
        fi
else
   echo "Not enough parameters.

Usage:
restore_incremental.sh master_backup.1.dar last_incremental_backup.1.dar /my/destination/folder/"
fi

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