1.centos伺服器忘記root密碼，登入伺服器，開啟/etc/my.cnf，新增skip_grant_tables

[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
#在my.ini，[mysqld]下新增一行，使其登入時跳過許可權檢查
skip_grant_tables
user=mysql

儲存後退出。

2.重新啟動mysql，如果提示“mysqld: unrecognized service”，則需要安裝mysql-server服務：yum -y install mysql-server,沒有提示直接重啟。

[root@cuishougt bin]#
 
 service mysqld restart
Stopping mysqld:                                           [  OK  ]
Starting mysqld:                                           [  OK  ]

3.這時再進入mysql是跳過密碼驗證的，提示輸入密碼時直接回車，然後更新root密碼，重新整理許可權後退出。

[root@cuishougt bin]# mysql -u root -p
Enter password: 
Welcome to the MySQL monitor.  Commands end
 
 with ; or \g.
Your MySQL connection id is 2
Server version: 5.1.73 Source distribution

Copyright (c) 2000, 2013, 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> 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> updates 
Display all 1105 possibilities? (y or n)
mysql> UPDATE user SET Password = password ( 'root' ) WHERE User = 'root' ;
Query OK, 3 rows affected (0.00 sec)
Rows matched: 3  Changed: 3  Warnings: 0

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

mysql> quit;

4.再次修改/etc/my.conf檔案，去掉或者註釋skip_grant_tables程式碼，然後重啟mysql服務，再次登入就可以用新密碼登入了。

[root@cuishougt bin]# service mysqld restart
Stopping mysqld:                                           [  OK  ]
Starting mysqld:                                           [  OK  ]
[root@cuishougt bin]# mysql -u root -p
Enter password: 
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: YES)
[root@cuishougt bin]# mysql -u root -p
Enter password: 
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 3
Server version: 5.1.73 Source distribution

5.windows下mysql8.0忘記root密碼重置方法如下

1）停止mysql服務

net stop mysql

2)輸入 mysqld --skip-grant-tables --shared-memory （第一個引數是跳過許可權檢查，第二個似乎是 MySQL 8 需要的）

mysqld --skip-grant-tables --shared-memory

3）重新開啟一個命名視窗登入mysql，這時不需要輸入密碼，直接回車進入mysql，選擇mysql庫，然後重置密碼

UPDATE mysql.user SET authentication_string=null WHERE User='root';
FLUSH PRIVILEGES;
ALTER USER 'root'@'localhost' IDENTIFIED WITH caching_sha2_password BY '123456';
FLUSH PRIVILEGES;
exit;

4）重啟mysql服務，這時就可以用新的密碼登入root賬戶了。