I use the following crontab record in order to daily backup my DB:
0 2 * * * MYSQL_PWD=password mysqldump -u user db_name > $HOME/db_backups/db_name-$(dat
Just create another cron:
0 3 * * * find $HOME/db_backups -name "db_name*.sql" -mtime +30 -exec rm {} \; >> $HOME/db_backups/purge.log 2>&1
It will find all backups older than 30 days and delete them.