Maybe updating the package the updater overwrote the root password.
To restore it:
Stop mysqld deamons.
$ sudo service mysqld stop
Go to mysql/bin directory
$ cd /usr/bin
Start a mysql deamon with this option:
$ sudo mysqld_safe --skip-grant-tables
Open another terminal and open a mysql session to execute this:
$ mysql
mysql> use mysql;
see Note1 below for next line.
mysql> UPDATE user SET authentication_string=PASSWORD(‘YOUR_NEW_PASSWORD_HERE‘) WHERE user = ‘root‘;
mysql> exit;
Now kill the mysqld_safe process and restart mysqld normally:
$ sudo service mysqld start
Note1: password is the column name in table mysql.user prior to version 5.7. After which it became authentication_string. Change your update statement accordingly.
如何你們看不懂，給我留言，我教你。
原文：http://www.cnblogs.com/vector11248/p/6680509.html