mysql的忘记密码、无法启动和socket文件丢失等错误问题的解决办法

问题一、忘记密码

[root@141 sh]# mysql -uroot -p
enter password: 
error 1045 (28000): access denied for user 'root'@'localhost' (using password: no)

解决方案：

在配置文件中选择免密登录：

[root@141 sh]# vim /etc/my.cnf

[root@141 sh]# mysql -uroot -p
enter password: 
welcome to the mariadb monitor.  commands end with ; or \g.
your mariadb connection id is 2
server version: 5.5.35-mariadb mariadb server

copyright (c) 2000, 2013, oracle, monty program ab and others.

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

mariadb [(none)]> exit

问题二、无法启动

解决方案：

# yum install mariadb-server -y //如果已安装可以省略  
# systemctl start mariadb.service //启动服务  
# systemctl enable mariadb.service //开机启动服务  
# mysql -u root -p //登录mysql  

问题三、socket文件丢失

连接localhost通常通过一个unix域套接字文件进行，一般是/tmp/mysql.sock。如果套接字文件被删除了，本地客户就不能连接。这可能发生在你的运行一个cron任务删除了/tmp下的临时文件。

如果你因为丢失套接字文件而不能连接，你可以简单地通过重启服务器重新创建得到它。因为服务器在启动时重新创建它。

接下来就是保存退出，然后确保这个目录存在，并且将这个目录的权限修改一下

chmod 777 /var/lib/mysql  
# service mysql  restart  
# service mysqld restart

root@izufkfljcz:/var/run/mysqld# mysql -uroot -p -s /var/run/mysqld/mysqld.sock   
enter password:   
welcome to the mysql monitor.  commands end with ; or \g.  
your mysql connection id is 4  
server version: 5.7.20-0ubuntu0.16.04.1 (ubuntu)  

copyright (c) 2000, 2017, 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> 

运行成功后，把之前改的配置改回来就行，之前的目录是/tmp/mysql.sock，建立一个软连接连上去就可以。

ln -s /var/run/mysqld/mysqld.sock /tmp/mysql.sock  

[root@141 sh]# mysql -uroot -p
enter password: 
welcome to the mariadb monitor.  commands end with ; or \g.
your mariadb connection id is 2
server version: 5.5.35-mariadb mariadb server

copyright (c) 2000, 2013, oracle, monty program ab and others.

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

成功！