恢复MySQL数据库密码步骤原理
停止Mysql服务程序
跳过授权表启动MySQL服务程序
重设root密码（更新user表记录）
以正常方式重启MySQL服务程序
密码恢复实例
例1：重置MySQL管理密码
首先停止已运行的MySQL服务程序
[root@host50 ~]# systemctl stop mysqld [root@host50 ~]# systemctl status mysqld ● mysqld.service - MySQL Server Loaded: loaded (/usr/lib/systemd/system/mysqld.service; enabled; vendor preset: disabled) Active: inactive (dead) since Tue 2019-07-02 03:54:56 CST; 6s ago Docs: man:mysqld(8) http://dev.mysql.com/doc/refman/en/using-systemd.html Process: 1426 ExecStart=/usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid $MYSQLD_OPTS (code=exited, status=0/SUCCESS) Process: 1083 ExecStartPre=/usr/bin/mysqld_pre_systemd (code=exited, status=0/SUCCESS) Main PID: 1430 (code=exited, status=0/SUCCESS) Jul 02 03:31:22 host50 systemd[1]: Starting MySQL Server... Jul 02 03:31:36 host50 systemd[1]: Started MySQL Server. Jul 02 03:54:55 host50 systemd[1]: Stopping MySQL Server... Jul 02 03:54:56 host50 systemd[1]: Stopped MySQL Server.
跳过授权表启动MySQL服务程序（配置--skip-grant-tables选项）见文档最后一行
[root@host50 ~]# vim /etc/my.cnf [mysqld] # # Remove leading # and set to the amount of RAM for the most important data # cache in MySQL. Start at 70% of total RAM for dedicated server, else 10%. # innodb_buffer_pool_size = 128M # # Remove leading # to turn on a very important data integrity option: logging # changes to the binary log between backups. # log_bin # # Remove leading # to set options mainly useful for reporting servers. # The server defaults are faster for transactions and fast SELECTs. # Adjust sizes as needed, experiment to find the optimal values. # join_buffer_size = 128M # sort_buffer_size = 2M # read_rnd_buffer_size = 2M datadir=/var/lib/mysql socket=/var/lib/mysql/mysql.sock secure_file_priv="/myload" # Disabling symbolic-links is recommended to prevent assorted security risks symbolic-links=0 default-storage-engine=innodb log-error=/var/log/mysqld.log pid-file=/var/run/mysqld/mysqld.pid skip_grant_tables=1
重连mysql后通过修改mysql库中user表中记录，做到重设root用户本机登录密码
[root@host50 ~]# systemctl restart mysqld
[root@host50 ~]# mysql -uroot
mysql> UPDATE mysql.user SET authentication_string=PASSWORD('123456')
-> WHERE user='root' AND host='localhost';
Query OK, 1 row affected, 1 warning (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 1
mysql> flush privileges;
Query OK, 0 rows affected (0.01 sec)
mysql> exit
注：通过执行“FLUSH PRIVILEGES;”可使授权表立即生效，对于正常运行的MySQL服务，也可以用上述方法来修改密码，不用重启服务。本例中因为是恢复密码，最好重启MySQL服务程序，所以上述“FLUSH PRIVILEGES;”操作可跳过。
重新以正常方式启动Mysql服务程序，验证新密码（可注释skip_grant_tables选项）
[root@host50 ~]# vim /etc/my.cnf [mysqld] #skip_grant_tables=1 . . . [root@host50 ~]# systemctl restart mysqld [root@host50 ~]# mysql -uroot ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO) [root@host50 ~]# mysql -uroot -p123456 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 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>
例2：重设Mysql管理用户密码（已知密码）
法一：使用mysqladmin管理工具，需要验证旧的密码
[root@host50 ~]# mysqladmin -u root -p password 'qaz123edc' Enter password: mysqladmin: [Warning] Using a password on the command line interface can be insecure. Warning: Since password will be sent to server in plain text, use ssl connection to ensure password safety.
法二：以root登录mysql后，使用set password指令设置（须先配置validate_password_policy=0）
mysql> set password for root@localhost=password('123456');
Query OK, 0 rows affected, 1 warning (0.00 sec)
法三：以root登录mysql后，使用grant授权工具设置
mysql> grant all on *.* to root@localhost identified by '123456'; Query OK, 0 rows affected, 1 warning (0.00 sec)
法四：以root登录MySQL后，使用update更新相应的表记录
mysql> update mysql.user set authentication_string=password('123456')
-> where user='root' and host='localhost';
Query OK, 0 rows affected, 1 warning (0.00 sec)
Rows matched: 1 Changed: 0 Warnings: 1