linux下mysql忘記密碼怎麼辦

前言

今天在服務器安裝mysql以後，登陸發現密碼錯誤，可是我沒有設置密碼呀，最後百度以後得知，mysql在5.7版本以後會自動建立一個初始密碼。
報錯以下:

[root@mytestlnx02 ~]# mysql -u root -p
Enter password: 
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: YES)

修改密碼

1. 檢查mysql服務是否啓動，若是啓動，關閉mysql服務

//查看mysql服務狀態
[root@mytestlnx02 ~]# ps -ef | grep -i mysql
root     22972     1  0 14:18 pts/0    00:00:00 /bin/sh /usr/bin/mysqld_safe --datadir=/var/lib/mysql --socket=/var/lib/mysql/mysql.sock --pid-file=/var/run/mysqld/mysqld.pid --basedir=/usr --user=mysql
mysql    23166 22972  0 14:18 pts/0    00:00:00 /usr/sbin/mysqld --basedir=/usr --datadir=/var/lib/mysql --plugin-dir=/usr/lib/mysql/plugin --user=mysql --log-error=/var/log/mysqld.log --pid-file=/var/run/mysqld/mysqld.pid --socket=/var/lib/mysql/mysql.sock
root     23237 21825  0 14:22 pts/0    00:00:00 grep -i mysql

//關閉服務
[root@mytestlnx02 ~]# service mysql stop
[root@mytestlnx02 ~]#

2. 修改mysql的配置文件my.cnf

my.cnf配置文件的位置，通常在/etc/my.cnf，有些版本在/etc/mysql/my.cnf

在配置文件中，增長2行代碼

[mysqld]

skip-grant-tables

做用是登陸mysql的時候跳過密碼驗證

而後啓動mysql服務，並進入mysql

[root@mytestlnx02 ~]# service mysqld start
[root@mytestlnx02 ~]#
[root@mytestlnx02 ~]# mysql -u root 
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
 
mysql>

3. 修改密碼

鏈接mysql這個數據庫，修改用戶密碼

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 mysql.user set authentication_string=password('root_password') where user='root';
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 (0.00 sec)
 
mysql> exit

4. 重啓mysql服務

先將以前加在配置文件裏面的2句代碼註釋或刪除掉，而後重啓mysql服務，就能夠使用剛剛設置的密碼登陸了。

[root@mytestlnx02 ~]# service mysql start
[root@mytestlnx02 ~]#
[root@mytestlnx02 ~]# mysql -u root -p
Enter password: 
Welcome to the MySQL monitor.  Commands end with ; or \g.

p.s.

在CentOS上的操做方式有所不一樣。

執行修改密碼的命令一直報錯

mysql> update user set authentication_string=password('xxxxxxxx') where User='root';       
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '('root_password') where User='root'' at line 1

不多是語法問題，檢查了不少遍，最後發現CentOS下應該這樣操做：

查看初始密碼

[root@VM_0_8_centos ~]# grep 'temporary password' /var/log/mysqld.log
2018-09-26T04:25:54.927944Z 5 [Note] [MY-010454] [Server] A temporary password is generated for root@localhost: DN34N/=?aIfZ

能夠看到初始密碼爲DN34N/=?aIfZ

使用初始密碼登陸

[root@VM_0_8_centos ~]# mysql -u root -p
Enter password: 
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 8
Server version: 8.0.12 MySQL Community Server - GPL

Copyright (c) 2000, 2018, Oracle and/or its affiliates. All rights reserved.

修改密碼

mysql> ALTER USER 'root' IDENTIFIED BY 'xxxxxxxxx';  
ERROR 1820 (HY000): You must reset your password using ALTER USER statement before executing this statement.
mysql> ALTER USER 'root'@'localhost' IDENTIFIED BY 'xxxxxxxx';
Query OK, 0 rows affected (0.11 sec)

mysql> flush privileges;
Query OK, 0 rows affected (0.01 sec)

mysql> exit
Bye

重啓服務就生效了

[root@VM_0_8_centos ~]# service mysqld stop 
Redirecting to /bin/systemctl stop  mysqld.service
[root@VM_0_8_centos ~]# service mysqld start
Redirecting to /bin/systemctl start  mysqld.service