忘記 root 密碼

1. 先關閉 mysqld 服務。
   

   [root@kvm6 ~]# /etc/init.d/mysqld stop
   Stopping mysqld:                                     [  OK  ]
   

2. mysqld_safe 跳過 grant tables，因為接著要下命令，所以讓其背景執行。
   

   [root@kvm6 ~]# mysqld_safe --skip-grant-tables &
   [1] 30343
   [root@kvm6 ~]# 190520 20:21:32 mysqld_safe Logging to '/var/log/mysqld.log'.
   190520 20:21:32 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql
   

3. 接著就可以免密碼登入 mysql 了。
   

   [root@kvm6 ~]# mysql -uroot
   Welcome to the MySQL monitor.  Commands end with ; or \g.
   Your MySQL connection id is 1
   Server version: 5.5.49 MySQL Community Server (GPL) by Remi
   
   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.
   

4. 使用 mysql 資料庫。
   

   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
   

5. 變更 root 密碼。
   

   mysql> update user set password=password("123qwe") where user='root';
   Query OK, 0 rows affected (0.00 sec)
   Rows matched: 3  Changed: 0  Warnings: 0
   

6. 更新權限。
   

   mysql> flush privileges;
   Query OK, 0 rows affected (0.00 sec)
   

7. 退出。
   

   mysql> quit
   Bye
   

8. 重新啟動 mysqld 服務。
   

   [root@kvm6 ~]# /etc/init.d/mysqld restart
   190520 20:22:55 mysqld_safe mysqld from pid file /var/run/mysqld/mysqld.pid ended
   Stopping mysqld:                                           [  OK  ]
   Starting mysqld:                                           [  OK  ]
   [1]+  Done                    mysqld_safe --skip-grant-tables