redhat5下安装MySQL-5.6，默认装完没有设置mysql的密码，按理说应该mysql的root用户的默认密码为空，但是默认空密码无法进入，报错信息如下：
Access denied for user 'root'@'localhost' (using password: NO)
各种密码尝试都无法进入mysql。经网上查找资料终于找到解决办法。
解决办法：
找到my.cnf文件，编辑文件，添加如下内容：
skip-grant-tables
skip-networking
红色字体为新添加。
[root@localhost /]# vi /usr/my.cnf
# For advice on how to change settings please see
# http://dev.mysql.com/doc/refman/5.6/en/server-configuration-defaults.html
[mysqld]
[color=red]
skip-grant-tables
skip-networking
[/color]
# Remove leading # and set to the amount of RAM for the most important data
# cache in MySQL. Start at 70% of total RAM for dedicated server, else10%.
# innodb_buffer_pool_size = 128M
# Remove leading # to turn on a very important data integrity option: logging
# changes to the binary log between backups.
# log_bin
# These are commonly set, remove the # and set as required.
# basedir = .....
重新启动：/etc/init.d/mysql restart
启动OK后，mysql的root用户默认空密码可以正常进入。
转自http://jadethao.iteye.com/blog/1922991