安装完mysql后就需要配置用户名和密码 (下面有老版本的修改方法)

需要共同的操作是跳过密码检测

修改MySQL的登录设置：
# vim /etc/my.cnf
在[mysqld]的段中加上一句：skip-grant-tables
例如：

[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
skip-grant-tables

保存并且退出vi。

重新启动mysqld

service mysqld restart

Stopping MySQL: [ OK ]
Starting MySQL: [ OK ]
下面是5.7版本所遇到的问题

mysql> update user set password=password(“新密码”) where user=”用户名”; 但是在执行语句的时候报错

ERROR 1054(42S22) Unknown column 'password' in ‘field list’
错误的原因是 5.7版本下的mysql数据库下已经没有password这个字段了，password字段改成了authentication_string

所以请使用一下命令

>mysql -u root -p
Enter password: ********
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 12
Server version: 5.7.18-log MySQL Community Server (GPL)

Copyright (c) 2000, 2017, 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;
Database changed
mysql> select User from user;  #此处为查询用户命令
+-----------+
| User      |
+-----------+
| *******  |
| mysql.sys |
| root      |
+-----------+
rows in set (0.00 sec)

mysql> update user set password=password("*******") where user="*******";  #修改密码报错
ERROR 1054 (42S22): Unknown column 'password' in 'field list'
mysql> update mysql.user set authentication_string=password('*******') where user='*******';  #修改密码成功
Query OK, 1 row affected, 1 warning (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 1

mysql> flush privileges;  #立即生效
Query OK, 0 rows affected (0.00 sec)

mysql> quit
Bye

n>mysql -u ******* -p #以该用户登录成功.
Enter password: ********
…………………………
mysql>

如果你需要开启远程访问，那就继续执行以下命令

GRANT ALL PRIVILEGES ON *.* TO 'root'@'%' IDENTIFIED BY 'your_root_password' WITH GRANT OPTION;

你可能会遇到以下问题：

ERROR 1820 (HY000): You must reset your password using ALTER USER statement before executing this statement.

又让你设置密码 接着修改

mysql> set password=password('your new password');
ERROR 1819 (HY000): Your password does not satisfy the current policy requirements

这样的提示是密码过于简单造成的，如果你执意要改，可以这样操作

mysql> set global validate_password_policy=0;
这个时候就大功告成了，有可能你还连接不上，注意一定要使用你在执行远程访问使用的密码，如果还是不行，就需要检查linux的防火墙，使用以下命令关闭

service iptables stop 关闭防火墙
service iptables start 打开防火墙
但是不推荐这样使用，因为不安全，你可以放行3306端口来使用Mysql的远程访问。

mysql 以前版本的修改方法

登录并修改MySQL的root密码

# mysql
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 3 to server version: 3.23.56
Type ‘help;’ or ‘\h’ for help. Type ‘\c’ to clear the buffer.
mysql> USE mysql ;
Database changed
mysql> UPDATE user SET Password = password ( ‘new-password’ ) WHERE User = ‘root’ ;
Query OK, 0 rows affected (0.00 sec)
Rows matched: 2 Changed: 0 Warnings: 0
mysql> flush privileges ;
Query OK, 0 rows affected (0.01 sec)
mysql> quit

将MySQL的登录设置修改回来

vim /etc/my.cnf

将刚才在[mysqld]的段中加上的skip-grant-tables删除
保存并且退出vim