http://sourceforge.net/projects/automysqlbackup/

cd /etc/mysql
wget http://garr.dl.sourceforge.net/sourceforge/automysqlbackup/automysqlbackup.sh.2.5

ln -s automysqlbackup.sh.2.5 backup-script
chmod 740 backup-script

vim backup-script

Next tell cron to run it 4 in the morning:

crontab -e

Add the following line:

0 4 * * * /etc/mysql/backup-script