使用apt-get 安装后的mysql 登录问题

当使用apt-get安装mysql后，ubuntu会自动生成一个用户名和密码。所以在第一次登陆时会报如下错误

ERROR 1045 (28000): Access denied for user 'db'@'localhost' (using password: NO)

而真正的用户名和密码在 /etc/mysql/debian.cnf

# Automatically generated for Debian scripts. DO NOT TOUCH!
[client]
host     = localhost
user     = debian-sys-maint
password = Y3fwpm731BnZtjry
socket   = /var/run/mysqld/mysqld.sock
[mysql_upgrade]
host     = localhost
user     = debian-sys-maint
password = Y3fwpm731BnZtjry
socket   = /var/run/mysqld/mysqld.sock
basedir  = /usr

此时进去后就是DBA 权限，那么就可以修改密码了。