#!/bin/bash

# config section
date=`date +%Y-%m-%d`
backup_dir='/mnt/mysql_backup'
retention=3

# create backup directory
mkdir -p $backup_dir

# database backup
for DB in $(mysql -e 'show databases' -sN|grep -v 'information_schema\|performance_schema'); do
  mysqldump $DB > "$backup_dir/$date.$DB.sql";
done

# delete old backups
find $backup_dir -type f -mtime +$retention -name '*.sql' -execdir rm -- '{}' \;