因後面會將作業系統從CentOS6.4升級到CentOS7，先試用下CentOS7。

1. 啟動容器服務

   systemctl start  docker.service

2. 下載CentOS7 映象

   [root@wxtest1607 ~]# docker pull centos:7.2.1511
   [root@wxtest1607 lixr]# docker images
   REPOSITORY                TAG                 IMAGE ID            CREATED             SIZE
   centos                    7.2.1511            686672a1d0cc        7 weeks ago         194.6 MB

   下載來源：https://hub.docker.com/
3. 登入docker中的CentOS7

   docker run -ti 6866 /bin/bash
   #6866 是 IMAGE ID 前四位數字-能區分出是哪個image即可
   root@b4ad1d1c87da /]# 
   #登入成功，接下來就可以為所欲為啦。

4. 檢查CentOS7系統

   root@b4ad1d1c87da  /]# uname -a
   Linux b4ad1d1c87da 3.10.0-327.el7.x86_64 #1 SMP Thu Nov 19 22:10:57 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux
   [root@b4ad1d1c87da /]# cat /etc/redhat-release 
   CentOS Linux release 7.2.1511 (Core)

5. 退出後 再進入CentOS7

   [root@wxtest1607 ~]# docker ps -a
   CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
   b4ad1d1c87da        6866                "/bin/bash"         12 seconds ago      Up 9 seconds                            mad_swanson
                  drunk_hypatia
   [root@wxtest1607 ~]# docker exec -ti b4ad /bin/bash
   [root@b4ad1d1c87da /]#