【Linux】【Mysql】ERROR 1698 (28000): Access denied for user ‘root‘@‘localhost‘

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工具：
mysql Ver 14.14 Distrib 5.7.25, for Linux (x86_64)

问题描述：
Ubuntu在安装完成mysql后，无法直接通过mysql -u root -p命令登录mysql，出现如下错误：ERROR 1698 (28000): Access denied for user ‘root’@‘localhost’

解决方法：

Ubuntu linux下安装新版本mysql，安装时root密码是随机的，因此会出现上述错误。

第一步，登录mysql

既然我们无法通过root用户进入MySQL，那我们就只能通过其他用户登录MySQL了。在我们下载安装MySQL的时候系统给我们创建了一个用户。打开 /etc/mysql/debian.cnf如下。

[email protected]:~$ sudo cat /etc/mysql/debian.cnf

[email protected]:~$ sudo cat /etc/mysql/debian.cnf 
# Automatically generated for Debian scripts. DO NOT TOUCH!
[client]
host     = localhost
user     = debian-sys-maint
password = 0NBFUVaaRF8KiZBD
socket   = /var/run/mysqld/mysqld.sock
[mysql_upgrade]
host     = localhost
user     = debian-sys-maint
password = 0NBFUVaaRF8KiZBD
socket   = /var/run/mysqld/mysqld.sock

我们找到client的user和password，然后在终端输入
mysql -u debian-sys-maint -p
然后回车输入 password的内容。这样就进入了MySQL了，如图：

[email protected]:~$ mysql -u debian-sys-maint -p
Enter password: 
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 3
Server version: 5.7.38-0ubuntu0.18.04.1 (Ubuntu)

Copyright (c) 2000, 2022, Oracle and/or its affiliates.

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.

第二步，查看user表

在mysql中输入：

select user, plugin from mysql.user，

结果如下：

+------------------+-----------------------+
| user             | plugin                |
+------------------+-----------------------+
| root             | auth_socket           |
| mysql.session    | mysql_native_password |
| mysql.sys        | mysql_native_password |
| debian-sys-maint | mysql_native_password |
+------------------+-----------------------+
4 rows in set (0.00 sec)

第三步，修改root密码

输入以下命令,其中123456是密码：

update mysql.user set authentication_string=PASSWORD('123456'), plugin='mysql_native_password' where user='root';

mysql> update mysql.user set authentication_string=PASSWORD('123456'), plugin='mysql_native_password' where user='root';
Query OK, 1 row affected, 1 warning (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 1

第四步，刷新

输入以下命令：

flush privileges;

然后重新启动服务器，就可以正常登录啦

sudo service mysql restart

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