mysql5.7密码忘记解决方法
ENV：
[root@centos7 ~]# uname -r
3.10.0-514.el7.x86_64
[root@centos7 ~]# cat /etc/redhat-release
CentOS Linux release 7.3.1611 (Core)
[root@centos7 ~]# rpm -qa mysql
[root@centos7 ~]# rpm -qa |grep mysql
mysql-community-common-5.7.26-1.el7.x86_64
mysql-community-client-5.7.26-1.el7.x86_64
mysql57-community-release-el7-11.noarch
mysql-community-server-5.7.26-1.el7.x86_64
mysql-community-libs-5.7.26-1.el7.x86_64
mysql-community-libs-compat-5.7.26-1.el7.x86_64
登陆时出错：
[root@centos7 ~]# mysql -u root -p
Enter password:
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO)密码忘记了（和刚安装后不知道密码一样）
网上有人说mysql的密码是空密码，其实在mysql5.7版本之后，密码不再是空密码了，
如果是刚安装的，可以在mysql的日志文件找到
grep 'temporary password' /var/log/mysqld.log补充：如果找到mysql提供的密码，可以使用
mysqladmin -u root -p 'mysql提供的密码' password ‘自己的新密码’
直接修改mysql的密码，但这种方法存在安全隐患，毕竟密码在命令行上显示了，不建议但不反对。
如果是忘记，修改如下：
1.修改 /etc/my.cnf,加入 skip-grant-tables;
[root@centos7 ~]# vim /etc/my.cnf空白位置加入，并保存退出；
[mysqld]
skip-name-resolve
skip-grant-tables[root@centos7 ~]# systemctl restart mysqld2.空密码直接进入mysql；
[root@centos7 ~]# mysql -u root -p
Enter password: (这里是空密码，直接回车)
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 2
Server version: 5.7.26 MySQL Community Server (GPL)
Copyright (c) 2000, 2019, 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> 进入mysql库；
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> 这里的mysql并不是没变，数据库位置是变化的；
3.修改密码：UPDATE user SET authentication_string=PASSWORD('newpassword') where USER='root';
mysql> UPDATE user SET authentication_string=PASSWORD('newpassword') where USER='root';
Query OK, 1 row affected, 1 warning (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 1
mysql>
mysql> FLUSH PRIVILEGES;
Query OK, 0 rows affected (0.00 sec)
mysql>4改回/etc/my.cnf
注释掉 ＃skip-grant-tables
[root@centos7 ~]# vim /etc/my.cnf[mysqld]
skip-name-resolve
#skip-grant-tables[root@centos7 ~]# systemctl restart mysqld5.用新的密码再进入mysql；
[root@centos7 ~]# mysql -u root -p
Enter password: (之前演示为newpassword)
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 6
Server version: 5.7.26
Copyright (c) 2000, 2019, 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>6.更改root密码，更改root密码： alter user 'root'@'localhost' identified by '密码';
修改用户密码；
ALTER USER testuser IDENTIFIED BY '123456';
修改当前登录用户
ALTER USER USER() IDENTIFIED BY '123456';
mysql> alter user user() identified by 'Linuxpassword!@#';
ERROR 1819 (HY000): Your password does not satisfy the current policy requirements
mysql> alter user user() identified by 'LINUX123password!@#';
Query OK, 0 rows affected (0.00 sec)
mysql> 可以看出，密码的复杂度有了很大的要求；
7.修改完成后就可以继续操作mysql了
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
+--------------------+
4 rows in set (0.00 sec)
mysql> exit
Bye