RedHat7 yum 安装Docker

AS7 安装Docker 很容易，但大家视乎都没有提到，yum 安装需要注册redhat developer user才行，系统需要链接OS 开发者订阅，否则无法获取安装包及附属包：
如果注册的用户没有开发者订阅权限，则无法用yum 安装：

[root@docker ~]# subscription-manager repos --list
This system has no repositories available through subscriptions.
[root@docker ~]# subscription-manager list                                    

+-------------------------------------------+
    Installed Product Status
+-------------------------------------------+
Product Name:   Red Hat Enterprise Linux Server
Product ID:     69
Version:        7.1
Arch:           x86_64
Status:         Not Subscribed
Status Details: Not supported by a valid subscription.
Starts:         
Ends:           

获取开发者订阅权限后（方法请参考：http://www.cnblogs.com/linuxprobe/p/5377830.html），重新登录：

[root@docker ~]# subscription-manager register [email protected] --password=*** --auto-attach --force
[root@docker ~]# subscription-manager list

+-------------------------------------------+
    Installed Product Status
+-------------------------------------------+
Product Name:   Red Hat Enterprise Linux Server
Product ID:     69
Version:        7.1
Arch:           x86_64
Status:         Subscribed
Status Details: 
Starts:         07/26/16
Ends:           07/26/17

[root@docker ~]# subscription-manager repos --enable=rhel-7-server-extras-rpms
Repository 'rhel-7-server-extras-rpms' is enabled for this system.

So, docker 的yum 源包是在rhel-7-server-extras-rpms。直接安装即可：

[root@docker ~]# yum install -y docker

done.