在預設情況下，mysql是禁止遠端連線的，而伺服器又不是隨隨便便就要登入的，所以就要開啟遠端連線。
開啟資料庫遠端連線的時候，記得要把伺服器的安全組也開放資料庫的埠（mysql預設3306），不然也會出現無法訪問的情況

建立遠端連線資料庫的使用者

1. 登入mysql

   [root@VM_149_46_centos etc]# mysql -u root -p
   Enter password: 
   Welcome to the MySQL monitor.  Commands end with ; or \g.
   Your MySQL connection id is 15
   Server version
    
   : 5.7.21 MySQL Community Server (GPL)
   
   Copyright (c) 2000, 2018, 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.

2. 建立遠端連線使用者

   mysql> use mysql
   Reading table information for completion of table and column names
   You can turn off this feature to get a quicker startup with -A
   
   Database changed
   
   mysql> CREATE USER 'cwm'@'%' IDENTIFIED BY 'Cwmniwo,1';
   Query OK, 0 rows affected (0.01 sec)

   為使用者建立一個數據庫試試

   mysql> CREATE DATABASE cwm1 DEFAULT CHARSET utf8 COLLATE utf8_general_ci;
   Query OK, 1 row affected (0.00 sec)

3. 授權

   mysql> GRANT ALL PRIVILEGES ON `cwm1`.* TO 'cwm'@'%' ;
   Query OK, 0 rows affected (0.00 sec)
   
   mysql> FLUSH PRIVILEGES;
   Query OK, 0 rows affected (0.00 sec)

4. 測試

   mysql> exit;
   Bye
   [root@VM_149_46_centos etc]# mysql -u cwm -p
   Enter password: 
   Welcome to the MySQL monitor.  Commands end with ; or \g.
   Your MySQL connection id is 16
   Server version: 5.7.21 MySQL Community Server (GPL)
   
   Copyright (c) 2000, 2018, 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> show databases;
   +--------------------+
   | Database           |
   +--------------------+
   | information_schema |
   | cwm1               |
   +--------------------+
   2 rows in set (0.00 sec)

   已經連線成功並可以查詢，經過測試，本地使用navicat也可以連線。

以下是修改配置檔案達到目的的步驟(請檢視參考連線進行配置)

1. 查詢配置檔案在哪裡
   先要查詢資料庫安裝在了哪裡

   [root@VM_149_46_centos etc]# which mysqld
   /usr/sbin/mysqld

   這裡可以得到資料庫安裝在了/usr/sbin/mysqld

   [root@VM_149_46_centos etc]# /usr/sbin/mysqld --verbose --help | grep -A 1 'Default options'
   Default options are read from the following files in the given order:
   /etc/my.cnf /etc/mysql/my.cnf /usr/etc/my.cnf ~/.my.cnf 

   這裡可以得出配置檔案的地址在 /etc/my.cnf、 /etc/mysql/my.cnf、 /usr/etc/my.cnf、 ~/.my.cnf

2. 修改配置檔案
3. 重啟資料庫服務
4. 測試