Ubuntu 14.04，更新一些软件之后莫名其妙的mysql无法登陆了，一直显示：“Access denied for user 'root'@'localhost'”
重置root密码后就好了，重置方法：
You have to reset the password! steps for mac osx(tested and working) and ubuntu
Stop MySQL
$ sudo service mysql stop
Start it in safe mode:
$ sudo mysqld_safe --skip-grant-tables
(above line is the whole command)
This will be an ongoing command until the process is finished so open another shell/terminal window, log in without a password:
$ mysql -u root
mysql> UPDATE mysql.user SET Password=PASSWORD('password') WHERE User='root';
Start MySQL
sudo service mysql start
your new password is 'password'.
参考自：
评论里说这么整不安全，帖子里还有更安全的方法，没有深究。
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这里是类似的问题：https://bugs.launchpad.net/ubuntu/+source/mariadb-10.0/+bug/1447808