针对不同方式安装mysql 5.7，密码修改方式不一样：
一。 rpm 方式安装，修改方法如下：
1、通过编辑/etc/my.cnf文件在[mysqld]下面加上skip-grant-tables=1,保存退出；
2、重启MySql服务【systemctl restart mysqld.service】；
3、以root身份登录MySql 【mysql -u root】;
4、进入mysql数据库【mysql> use mysql;】;
5、修改root密码：
mysql>update user set authentication_string=password('root123'),password_last_changed=now() where user='root';
6、退出mysql,再次编辑/etc/my.cnf文件，将第一步中添加的skip-grant-tables=1删掉，重启启动MySql服务即可。
二。 tar 包编译安装
root@INT03 mysql]# bin/mysql -uroot -p
Enter password:
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: YES)
#################################################################################################
[root@INT03 mysql]# service mysqld stop
Shutting down MySQL.. SUCCESS!
[root@INT03 mysql]# bin/mysqld_safe --skip-grant-tables &
[1] 8006
[root@INT03 mysql]# 2016-11-01T09:19:06.934367Z mysqld_safe Logging to '/data/mysql/error.log'.
2016-11-01T09:19:06.953025Z mysqld_safe Starting mysqld daemon with databases from /data/mysql
[root@INT03 mysql]# bin/mysql -p //无需密码直接回车进去
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 2
Server version: 5.7.13-log MySQL Community Server (GPL)
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> desc mysql.user；
+------------------------+-----------------------------------+------+-----+-----------------------+-------+
| Field | Type | Null | Key | Default | Extra |
+------------------------+-----------------------------------+------+-----+-----------------------+-------+
| Host | char(60) | NO | PRI | | |
| User | char(32) | NO | PRI | | |
| Select_priv | enum('N','Y') | NO | | N | |
| Insert_priv | enum('N','Y') | NO | | N | |
| Update_priv | enum('N','Y') | NO | | N | |
| Delete_priv | enum('N','Y') | NO | | N | |
| Create_priv | enum('N','Y') | NO | | N | |
| Drop_priv | enum('N','Y') | NO | | N | |
| Reload_priv | enum('N','Y') | NO | | N | |
| Shutdown_priv | enum('N','Y') | NO | | N | |
| Process_priv | enum('N','Y') | NO | | N | |
| File_priv | enum('N','Y') | NO | | N | |
| Grant_priv | enum('N','Y') | NO | | N | |
| References_priv | enum('N','Y') | NO | | N | |
| Index_priv | enum('N','Y') | NO | | N | |
| Alter_priv | enum('N','Y') | NO | | N | |
| Show_db_priv | enum('N','Y') | NO | | N | |
| Super_priv | enum('N','Y') | NO | | N | |
| Create_tmp_table_priv | enum('N','Y') | NO | | N | |
| Lock_tables_priv | enum('N','Y') | NO | | N | |
| Execute_priv | enum('N','Y') | NO | | N | |
| Repl_slave_priv | enum('N','Y') | NO | | N | |
| Repl_client_priv | enum('N','Y') | NO | | N | |
| Create_view_priv | enum('N','Y') | NO | | N | |
| Show_view_priv | enum('N','Y') | NO | | N | |
| Create_routine_priv | enum('N','Y') | NO | | N | |
| Alter_routine_priv | enum('N','Y') | NO | | N | |
| Create_user_priv | enum('N','Y') | NO | | N | |
| Event_priv | enum('N','Y') | NO | | N | |
| Trigger_priv | enum('N','Y') | NO | | N | |
| Create_tablespace_priv | enum('N','Y') | NO | | N | |
| ssl_type | enum('','ANY','X509','SPECIFIED') | NO | | | |
| ssl_cipher | blob | NO | | NULL | |
| x509_issuer | blob | NO | | NULL | |
| x509_subject | blob | NO | | NULL | |
| max_questions | int(11) unsigned | NO | | 0 | |
| max_updates | int(11) unsigned | NO | | 0 | |
| max_connections | int(11) unsigned | NO | | 0 | |
| max_user_connections | int(11) unsigned | NO | | 0 | |
| plugin | char(64) | NO | | mysql_native_password | |
| authentication_string | text | YES | | NULL | |
| password_expired | enum('N','Y') | NO | | N | |
| password_last_changed | timestamp | YES | | NULL | |
| password_lifetime | smallint(5) unsigned | YES | | NULL | |
| account_locked | enum('N','Y') | NO | | N | |
+------------------------+-----------------------------------+------+-----+-----------------------+-------+
45 rows in set (0.00 sec)
mysql> update mysql.user set authentication_string=password('123456') where user='root' and host='localhost';
Query OK, 1 row affected, 1 warning (0.07 sec)
Rows matched: 1 Changed: 1 Warnings: 1
mysql> flush privileges;
Query OK, 0 rows affected (0.06 sec)
mysql> exit
Bye
[root@INT03 mysql]# service mysqld restart
Shutting down MySQL..2016-11-01T09:23:55.348080Z mysqld_safe mysqld from pid file /data/mysql/INT03.pid ended
SUCCESS!
Starting MySQL. SUCCESS!
[1]+ Done bin/mysqld_safe --skip-grant-tables
[root@INT03 mysql]# mysql -uroot -p
-bash: mysql: command not found
[root@INT03 mysql]# bin/mysql -uroot -p
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 2
Server version: 5.7.13-log
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> show databases;
ERROR 1820 (HY000): You must reset your password using ALTER USER statement before executing this statement.
mysql> alter user 'root'@'localhost' identified by 'A123456';
Query OK, 0 rows affected (0.04 sec)
mysql> exit
Bye
