[root@localhost ~]# vim /etc/my.cnf    '进入到配置文件'
[mysqld]
user = mysql
basedir = /usr/local/mysql
datadir=/usr/local/mysql/data
port = 3306
character_set_server=utf8
pid-file = /usr/local/mysql/mysqld.pid
socket = /usr/local/mysql/mysql.sock
server-id = 1
skip-grant-tables            '添加此行'
[root@localhost ~]# systemctl restart mysqld 


[root@localhost ~]# mysql    '再次登录发现不需要密码了'
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 3
Server version: 5.7.17 Source distribution

Copyright (c) 2000, 2016, 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> 

mysql> desc mysql.user;  '查看密码字段'

authentication_string    '此字段就是密码字段  当然这一步是在你记不住密码字段的情况下'
mysql> select user,host,authentication_string from mysql.user;   '查看登录名  登录终端  密码'
+-----------+-----------+-------------------------------------------+
| user      | host      | authentication_string                     |
+-----------+-----------+-------------------------------------------+
| root      | localhost | *7A8BBCB18A250055A6BB98ECFA33A8174D219504 |
| mysql.sys | localhost | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE |
| root      | %         | *6691484EA6B50DDDE1926A220DA01FA9E575C18A |
+-----------+-----------+-------------------------------------------+
3 rows in set (0.00 sec)
mysql> update mysql.user set authentication_string=password('Abc123') where user='root'     'updata  跟新表内容  user表 当user为root的情况下  将其密码设置为Abc123'
    -> ;
Query OK, 1 row affected, 1 warning (0.01 sec)
Rows matched: 2  Changed: 1  Warnings: 1

[root@localhost ~]# vim /etc/my.cnf
#skip-grant-tables   '将刚才的字段进行注释'
[root@localhost ~]# systemctl restart mysqld    '每次更改完文件都要进行重启服务'


[root@localhost ~]# mysql     '再次登录发现需要验证密码了'  
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO)
[root@localhost ~]# mysql -u root -p"Abc123"   '用刚刚设置的密码再次尝试登录'
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 4
Server version: 5.7.17 Source distribution

Copyright (c) 2000, 2016, 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> 

[ root@mysql1 ~ ]# vim /etc/my.cnf
[mysqld]
skip-grant-tables
[root@mysql1 ~]# service mysqld restart
[root@mysql1 ~ ]# mysql
mysql> update mysql.user set passvord=password("456") where user="root" and host="localhost";
mysql> flush privileges;  '刷新一下表'
mysql> \q
[root@mysql1 ~]# vim /etc/my.cnf
[mysqld]
# skip-grant-table
[root@mysql1 ~]# service mysqld restart