解决MariaDB无密码就可以登录的问题

问题：

使用apt-get来安装mysql，安装好之后发现安装的是 MariaDB，如下，无需密码既可以登录了。即使使用mysqladmin设置好密码，用密码登录可以，不用密码登录也可以

root@ubuntu:/etc/mysql# mysql
Welcome to the MariaDB monitor. Commands end with ; or \g.
Your MariaDB connection id is 35
Server version: 10.0.31-MariaDB-0ubuntu0.16.04.2 Ubuntu 16.04
Copyright (c) 2000, 2017, Oracle, MariaDB Corporation Ab and others.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

排查思路：

第一看看my.conf有没有skip-grant-tables，跳过密码验证

过滤了下没有

看看my.cnf里面是不是把密码写进去了，查找了相关.cnf文件去看了看也没有

root@ubuntu:~# find / -name "*.cnf"
/usr/share/ssl-cert/ssleay.cnf
/usr/share/dovecot/dovecot-openssl.cnf
/usr/lib/ssl/openssl.cnf
/etc/ssl/openssl.cnf
/etc/alternatives/my.cnf
/etc/mysql/my.cnf
/etc/mysql/mariadb.cnf
/etc/mysql/conf.d/mysqldump.cnf
/etc/mysql/conf.d/mysql.cnf
/etc/mysql/mariadb.conf.d/50-mysqld_safe.cnf
/etc/mysql/mariadb.conf.d/50-mysql-clients.cnf
/etc/mysql/mariadb.conf.d/50-client.cnf
/etc/mysql/mariadb.conf.d/50-server.cnf
/etc/mysql/debian.cnf
/var/lib/dpkg/alternatives/my.cnf
root@ubuntu:~#

不过有个小发现：

vim /etc/mysql/debian.cnf
# Automatically generated for Debian scripts. DO NOT TOUCH!
[client]
host = localhost
user = root
password =
socket = /var/run/mysqld/mysqld.sock
[mysql_upgrade]
host = localhost
user = root
password =
socket = /var/run/mysqld/mysqld.sock
basedir = /usr

看了说明是以上由脚本生成，不要改动，虽然这样写，我也去改了下，加上密码，重启还是不行

最后的最后，去搜索了很久，终于有发现了，是用户插件问题。

第一我去跟安装正常的mysql来比较下，如下

看到这里应该发现问题了，按照正常的修改就行了

sudo service mysql stop
sudo mysqld_safe --skip-grant-tables

进去mysql执行如下命令：

MariaDB [(none)]> UPDATE mysql.user SET authentication_string = PASSWORD('mypassword'), plugin = 'mysql_native_password' WHERE User = 'root' AND Host = 'localhost';
MariaDB [(none)]> FLUSH PRIVILEGES;

验证：

先kill掉mysql kill -9 pid

启动：

sudo service mysql start

最后验证下：需要密码了

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