初次安装MySQL默认没有密码，安装完毕之后最好增加密码
1、命令
1 #/usr/bin/mysqladmin -u root password 'new-password'
格式：mysqladmin -u 用户名 -p 旧密码 password 新密码
2、例子
例1：给root加个密码admin
键入以下命令 ：
1 [root@node1]# /usr/bin/mysqladmin -u root password admin
注：因为开始时root没有密码，所以-p旧密码一项就可以省略了。
3、测试是否修改成功
1）不用密码登录
1 [root@node1 /]# mysql
2 ERROR 1045: Access denied for user: 'root@localhost' (Using password: NO)
显示错误，说明密码已经修改。
2）用修改后的密码登录
1 [root@node1 /]# mysql -u root -p 2 Enter password: (输入修改后的密码admin) Welcome to the MariaDB monitor. Commands end with ; or g.
Your MariaDB connection id is 7
Server version: 5.5.60-MariaDB MariaDB Server
Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.
Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.
MariaDB [(none)]>
成功！
这是通过mysqladmin命令修改口令，也可通过修改库来更改口令。
4）使用SQL语句再次修改密码
1 [root@node1 /]# mysql -u root -p 2 Enter password: （输入修改后的密码admin）
Welcome to the MariaDB monitor. Commands end with ; or g.
Your MariaDB connection id is 28
Server version: 5.5.60-MariaDB MariaDB Server
Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.
Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.
MariaDB [(none)]> 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
MariaDB [mysql]> set password=password('123456');
Query OK, 0 rows affected (0.00 sec)
MariaDB [mysql]> exit
Bye
5）用再次修改后的密码登录
1 [root@node1 /]# mysql -u root -p 2 Enter password: （输入再次修改后的密码）
Welcome to the MariaDB monitor. Commands end with ; or g.
Your MariaDB connection id is 29
Server version: 5.5.60-MariaDB MariaDB Server
Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.
Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.
MariaDB [(none)]>
登录成功！
6）使用linux命令再次修改密码
1 [root@node1 /]# mysqladmin -u root -p password abcdef （这里abcdef是新密码） 2 Enter password: （输入上一次的密码）
7）使用新密码登录
1 [root@node1 /]# mysql -u root -p 2 Enter password: （使用新密码）
Welcome to the MariaDB monitor. Commands end with ; or g.
Your MariaDB connection id is 35
Server version: 5.5.60-MariaDB MariaDB Server
Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.
Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.
MariaDB [(none)]>
登录成功！