centos use docker install mysql

1. docker pull 镜像
   $ docker pull mysql:5.7.17

2. 创建容器实例
   $ docker run --name mysqldb -p 3306:3306 -e MYSQL_ROOT_PASSWORD=***** -d mysql:5.7.17

使用客户端连接mysql 报错：2005 unknow mysqlserver host

3. 进入容器实例进行测试
   $ docker exec -it 2a7a85124400 /bin/bash

4. 连接数据库
   $ mysql -h 127.0.0.1 -u root -p

root@cf9f8da7d928:~# mysql -h 127.0.0.1 -u root -p
Enter password:
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 5
Server version: 5.7.17 MySQL Community Server (GPL)

Copyright (c) 2000, 2016, 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.

5. 在容器实例中测试连接没有问题，于是考虑防火墙问题，是否没有开放 3306 端口。

6. 防火墙配置：开启3306端口

7. 使用客户端重新连接mysql。