解决 MariaDB无密码就可以登录的问题

问题：

困扰了很久的问题，，

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

1 root@ubuntu:/etc/mysql# mysql
2 Welcome to the MariaDB monitor.  Commands end with ; or \g.
3 Your MariaDB connection id is 35
4 Server version: 10.0.31-MariaDB-0ubuntu0.16.04.2 Ubuntu 16.04
5 
6 Copyright (c) 2000, 2017, Oracle, MariaDB Corporation Ab and others.
7 
8 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

 1 root@ubuntu:~# cd /etc/mysql/
 2 root@ubuntu:/etc/mysql# pwd
 3 /etc/mysql
 4 root@ubuntu:/etc/mysql# ls -l
 5 总用量 36
 6 drwxr-xr-x 2 root root 4096 12月  7 18:05 conf.d
 7 -rw------- 1 root root  277 12月  7 17:31 debian.cnf
 8 -rw------- 1 root root  317 12月  7 17:05 debian.cnf-5.7
 9 -rwxr-xr-x 1 root root 1426 7月   1 04:26 debian-start
10 -rw-r--r-- 1 root root  869 7月   1 04:26 mariadb.cnf
11 drwxr-xr-x 2 root root 4096 12月  7 18:08 mariadb.conf.d
12 lrwxrwxrwx 1 root root   24 12月  7 17:18 my.cnf -> /etc/alternatives/my.cnf
13 -rw-r--r-- 1 root root  839 1月  22  2017 my.cnf.fallback
14 -rw-r--r-- 1 root root  682 2月   4  2017 mysql.cnf
15 drwxr-xr-x 2 root root 4096 12月  7 18:08 mysql.conf.d
16 root@ubuntu:/etc/mysql# grep "skip-grant-tables"  -r
17 root@ubuntu:/etc/mysql# 

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

 1 root@ubuntu:~# find / -name "*.cnf"
 2 /usr/share/ssl-cert/ssleay.cnf
 3 /usr/share/dovecot/dovecot-openssl.cnf
 4 /usr/lib/ssl/openssl.cnf
 5 /etc/ssl/openssl.cnf
 6 /etc/alternatives/my.cnf
 7 /etc/mysql/my.cnf
 8 /etc/mysql/mariadb.cnf
 9 /etc/mysql/conf.d/mysqldump.cnf
10 /etc/mysql/conf.d/mysql.cnf
11 /etc/mysql/mariadb.conf.d/50-mysqld_safe.cnf
12 /etc/mysql/mariadb.conf.d/50-mysql-clients.cnf
13 /etc/mysql/mariadb.conf.d/50-client.cnf
14 /etc/mysql/mariadb.conf.d/50-server.cnf
15 /etc/mysql/debian.cnf
16 /var/lib/dpkg/alternatives/my.cnf
17 root@ubuntu:~# 

不过有个小发现，

 1  vim /etc/mysql/debian.cnf
 2 # Automatically generated for Debian scripts. DO NOT TOUCH!
 3 [client]
 4 host     = localhost
 5 user     = root
 6 password = 
 7 socket   = /var/run/mysqld/mysqld.sock
 8 [mysql_upgrade]
 9 host     = localhost
10 user     = root
11 password = 
12 socket   = /var/run/mysqld/mysqld.sock
13 basedir  = /usr
14 
15 看了说明是以上由脚本生成，不要改动，
16 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google了很久，终于有发现了,是用户插件问题。

参见这里：https://nixmash.com/post/fix-for-mysql-rootlocalhost-access-denied-on-new-installs

第一我去跟安装正常的mysql来比较下，如下

1 正常mysql
2 mysql> select user, plugin from mysql.user where plugin = 'mysql_native_password';
3 +-----------+-----------------------+
4 | user      | plugin                |
5 +-----------+-----------------------+
6 | root      | mysql_native_password |
7 +-----------+-----------------------+
8 8 rows in set (0.00 sec)

1 不正常的
2 
3 MariaDB [(none)]> select user, plugin from mysql.user;
4 +------+-------------+
5 | user | plugin      |
6 +------+-------------+
7 | root | unix_socket |
8 +------+-------------+
9 1 row in set (0.00 sec)

看到这里应该发现问题了，按照正常的修改就行了

如下：

 1 sudo service mysql stop
 2 sudo mysqld_safe --skip-grant-tables
 3 进去mysql执行如下命令：
 4 MariaDB [(none)]> UPDATE mysql.user SET authentication_string = PASSWORD('mypassword'), plugin = 'mysql_native_password' WHERE User = 'root' AND Host = 'localhost';
 5 MariaDB [(none)]> FLUSH PRIVILEGES;
 6 验证：
 7 MariaDB [(none)]> select user, plugin from mysql.user
 8     -> ;
 9 +------+-----------------------+
10 | user | plugin                |
11 +------+-----------------------+
12 | root | mysql_native_password |
13 +------+-----------------------+
14 1 row in set (0.01 sec)
15 
16 先杀死mysql  kill -9 pid
17 启动：
18 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:~#