linux下mysql的root密码忘记解决方法

1．首先确认服务器出于安全的状态，也就是没有人能够任意地连接MySQL数据库。 

因为在重新设置MySQL的root密码的期间，MySQL数据库完全出于没有密码保护的 
状态下，其他的用户也可以任意地登录和修改MySQL的信息。可以采用将MySQL对 
外的端口封闭，并且停止Apache以及所有的用户进程的方法实现服务器的准安全 
状态。最安全的状态是到服务器的Console上面操作，并且拔掉网线。 
2．修改MySQL的登录设置： 
# vi /etc/my.cnf 
在[mysqld]的段中加上一句：skip-grant-tables 
例如： 
[mysqld] 
datadir=/var/lib/mysql 
socket=/var/lib/mysql/mysql.sock 
skip-grant-tables 
保存并且退出vi。 
3．重新启动mysqld 
# /etc/init.d/mysqld restart 
Stopping MySQL: [ OK ] 
Starting MySQL: [ OK ] 
4．登录并修改MySQL的root密码 
# /usr/bin/mysql 
Welcome to the MySQL monitor. Commands end with ; or \g. 
Your MySQL connection id is 3 to server version: 3.23.56 
Type 'help;' or '\h' for help. Type '\c' to clear the buffer. 
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> UPDATE user SET Password = password ( 'new-password' ) WHERE User = 'root' ; 
Query OK, 0 rows affected (0.00 sec) 
Rows matched: 2 Changed: 0 Warnings: 0 
mysql> flush privileges ; 
Query OK, 0 rows affected (0.01 sec) 
mysql> quit 
Bye 
5．将MySQL的登录设置修改回来 
# vi /etc/my.cnf 
将刚才在[mysqld]的段中加上的skip-grant-tables删除 
保存并且退出vi。 
6．重新启动mysqld 
# /etc/init.d/mysqld restart 
Stopping MySQL: [ OK ] 
Starting MySQL: [ OK ]

《FROM:http://www.cnblogs.com/allenblogs/archive/2010/08/12/1798247.html》

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另外一种破解root或其它帐号密码的方法：

打开一个终端窗口，输入mysqld_safe --skip-grant-tables

[root@rhel2 mysql]# mysqld_safe --skip-grant-tables
170918 15:18:05 mysqld_safe Logging to '/var/log/mariadb/mariadb.log'.
170918 15:18:05 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql

再打开另外一个窗口，输入mysql后不用输入密码就能直接登录进去，然后修改user表里用户的密码。

[root@rhel2 ~]# mysql
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MariaDB connection id is 1
Server version: 5.5.56-MariaDB MariaDB Server

Copyright (c) 2000, 2017, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

MariaDB [(none)]> 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
MariaDB [mysql]> select user();
+--------+
| user() |
+--------+
| root@  |
+--------+
1 row in set (0.00 sec)

MariaDB [mysql]> select host,user,password from user;
+-----------+------+-------------------------------------------+
| host      | user | password                                  |
+-----------+------+-------------------------------------------+
| localhost | root | *09205D393DCDFAFF76E0D479E00C71C2F090C606 |
| 127.0.0.1 | root | *09205D393DCDFAFF76E0D479E00C71C2F090C606 |
| ::1       | root | *09205D393DCDFAFF76E0D479E00C71C2F090C606 |
+-----------+------+-------------------------------------------+
3 rows in set (0.00 sec)

MariaDB [mysql]> update user set password=password('123456') where user='root';
Query OK, 3 rows affected (0.00 sec)
Rows matched: 3  Changed: 3  Warnings: 0

MariaDB [mysql]> select host,user,password from user;
+-----------+------+-------------------------------------------+
| host      | user | password                                  |
+-----------+------+-------------------------------------------+
| localhost | root | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
| 127.0.0.1 | root | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
| ::1       | root | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
+-----------+------+-------------------------------------------+
3 rows in set (0.00 sec)

MariaDB [mysql]> 

修改完成后，直接关闭第一个窗口。然后重启mariadb，使用新密码登录。