因后面会将操作系统从CentOS6.4升级到CentOS7，先试用下CentOS7。

1. 启动容器服务

   systemctl start  docker.service

2. 下载CentOS7 镜像

   [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

   下载来源：https://hub.docker.com/
3. 登录docker中的CentOS7

   docker run -ti 6866 /bin/bash
   #6866 是 IMAGE ID 前四位数字-能区分出是哪个image即可
   root@b4ad1d1c87da /]# 
   #登录成功，接下来就可以为所欲为啦。

4. 检查CentOS7系统

   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. 退出后 再进入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 /]#