1、# service mysqld stop  #停止mysql数据库服务
Shutting down MySQL.. SUCCESS! 
2、# service mysqld start --skip-grant-tables #跳过授权表启动mysql数据库服务（注：参数--skip-grant-tables为跳过授权表）
Starting MySQL.... SUCCESS!
3、# mysql -p    #进入mysql数据库添加root用户并授权
Enter password:      #此处直接回车，不用输密码
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.6.26-log Source distribution

Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> use mysql;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
mysql> select host,user from user;
+----------+-------+
| host     | user  |
+----------+-------+
| 10.0.0.% | nginx |
| 10.0.0.0 | nginx |
+----------+-------+
2 rows in set (0.03 sec)
mysql> update user set password=password("new_password") where user="root";  
Query OK, 0 rows affected (0.16 sec)
Rows matched: 0  Changed: 0  Warnings: 0
mysql> insert into user set user='root',ssl_cipher='',x509_issuer='',x509_subject='';  #插入root用户
Query OK, 1 row affected (0.03 sec)
mysql> select host,user from user;   #查询添加root用户是否成功
+----------+-------+
| host     | user  |
+----------+-------+
|          | root  |
| 10.0.0.% | nginx |
| 10.0.0.0 | nginx |
+----------+-------+
3 rows in set (0.00 sec)
mysql> update user set Host='localhost',select_priv='y', insert_priv='y',update_priv='y',Alter_priv='y',delete_priv='y',create_priv='y',drop_priv='y',reload_priv='y',shutdown_priv='y',Process_priv='y',file_priv='y',grant_priv='y',References_priv='y',index_priv='y',create_user_priv='y',show_db_priv='y',super_priv='y',create_tmp_table_priv='y',Lock_tables_priv='y',execute_priv='y',repl_slave_priv='y',repl_client_priv='y',create_view_priv='y',show_view_priv='y',create_routine_priv='y',alter_routine_priv='y',create_user_priv='y' where user='root';                                #更新root用户权限
Query OK, 1 row affected (0.12 sec)
Rows matched: 1  Changed: 1  Warnings: 0
mysql> exit
Bye
4、# service mysqld restart       #重新启动mysql数据库
Shutting down MySQL.. SUCCESS! 
Starting MySQL..... SUCCESS! 
5、# mysql_secure_installation  #进入mysql数据库设置root用户密码

NOTE: RUNNING ALL PARTS OF THIS SCRIPT IS RECOMMENDED FOR ALL MySQL
      SERVERS IN PRODUCTION USE!  PLEASE READ EACH STEP CAREFULLY!

In order to log into MySQL to secure it, we'll need the current
password for the root user.  If you've just installed MySQL, and
you haven't set the root password yet, the password will be blank,
so you should just press enter here.

Enter current password for root (enter for none): 
OK, successfully used password, moving on...

Setting the root password ensures that nobody can log into the MySQL
root user without the proper authorisation.

Set root password? [Y/n] y             #此处询问是否修改root用户密码，输入"y"后回车，给前面添加的root用户设置密码
New password: 
Re-enter new password: 
Password updated successfully!    #提示root用户密码修改成功
Reloading privilege tables..
 ... Success!

#以下为mysql数据库的一些安全优化
By default, a MySQL installation has an anonymous user, allowing anyone
to log into MySQL without having to have a user account created for
them.  This is intended only for testing, and to make the installation
go a bit smoother.  You should remove them before moving into a
production environment.

Remove anonymous users? [Y/n] y
 ... Success!

Normally, root should only be allowed to connect from 'localhost'.  This
ensures that someone cannot guess at the root password from the network.

Disallow root login remotely? [Y/n] y
 ... Success!

By default, MySQL comes with a database named 'test' that anyone can
access.  This is also intended only for testing, and should be removed
before moving into a production environment.

Remove test database and access to it? [Y/n] y
 - Dropping test database...
 ... Success!

Reloading the privilege tables will ensure that all changes made so far
will take effect immediately.

Reload privilege tables now? [Y/n] y
 ... Success!

All done!  If you've completed all of the above steps, your MySQL
installation should now be secure.

Thanks for using MySQL!

Cleaning up...

6、验证前面5步操作是否有效
# mysql -uroot -p  #此时不输入正确的root用户密码，已经提示错误，不能登录         
Enter password: 
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO)
# mysql -uroot -p 
Enter password:     #再次输入正确的root用户密码后，进入数据库，代表root用户添加成功，并成功修改密码，如下所示：
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 15
Server version: 5.6.26-log Source distribution

Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| bbs                |
| blog               |
| mysql              |
| performance_schema |
| www                |
+--------------------+
6 rows in set (0.08 sec)

mysql> use mysql;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
mysql> select host,user from user;
+-----------+-------+
| host      | user  |
+-----------+-------+
| 10.0.0.%  | nginx |
| 10.0.0.0  | nginx |
| localhost | root  |  #代表root用户添加成功
+-----------+-------+
3 rows in set (0.00 sec)

mysql> exit

Bye

本文转自 linuxzkq 51CTO博客，原文链接:http://blog.51cto.com/linuxzkq/1693991