ubuntu下非交互式安装MySQL
$ sudo su -
# MYSQL_PASS=nova 设定mysql的密码和nova数据库的密码
# cat <<MYSQL_PRESEED | debconf-set-selections
>mysql-server-5.5 mysql-server/root_password password $MYSQL_PASS
>mysql-server-5.5 mysql-server/root_password_again password $MYSQL_PASS
>mysql-server-5.5 mysql-server/start_on_boot boolean true
>MYSQL_PRESEED
# apt-get install -y mysql-server