ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO)

Centos7.5  刚安装的mariadb数据库报错

报错:

ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO)

原因一:没有启动数据库

解决方法:
    systemctl start mariadb
    systemctl enable mariadb

原因二:未知

解决方法:
[root@db01 ~]# vim /etc/my.cnf
[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
skip-grant-tables  #在配置文件中加入这一条
[root@db01 ~]# systemctl restart mariadb    #重启数据库
[root@db01 ~]# mysql  #登录成功
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MariaDB connection id is 2
Server version: 5.5.60-MariaDB MariaDB Server

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

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

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