一、前言
最近在一个集群上安装 Docker，本来多么简单的事却因为网络原因以及系统版本变得曲折了，也由于找到了不适合的解决方案，饶了一个弯，所以特此记录一下安装过程，防止重复踩坑。
==系统版本：Centos 7.2.1511==
二、下载与上传
由于服务器不能连接外网，所以服务器使用的是公司自带的 yum 仓库，但是仓库内没有 Docker 安装包，所以需要自己下载。
下载地址：https://yum.dockerproject.org/repo/main/centos/7/Packages/
下载文件：
下载完成后，上传到服务器等待安装
三、安装
依次输入如下命令：
$ sudo yum -y localinstall docker-engine-selinux-1.13.1-1.el7.centos.noarch.rpm
$ sudo yum -y localinstall docker-engine-1.13.1-1.el7.centos.x86_64.rpm
这里使用yum -y localinstall命令，而不是rpm -ivh，是因为它会自动从仓库中下载并安装相应的依赖包，那么如果指定的仓库中有系统对应的版本，安装就应该是没问题的，但是我所使用的仓库中没有7.2.1511版本的安装包，在该目录下有一个readme文件（通过浏览器打开），内容如下：
This directory (and version of CentOS) is deprecated. For normal users,you should use /7/ and not /7.2.1511/ in your path. Please see this FAQ
concerning the CentOS release scheme:
https://wiki.centos.org/FAQ/General
If you know what you are doing,and absolutely want to remain at the 7.2.1511
level,go to http://vault.centos.org/ for packages.
Please keep in mind that 7.2.1511 no longer gets any updates,nor
any security fix's.
嗯，大概意思就是让我使用版本7目录下的…
==由于对应版本的安装包不存在时发生的异常见附录1==
四、修改 yum 获取的版本
使用如下命令进入修改界面：
sudo vi /etc/yum.repos.d/CentOS-Base.repo
原文件如下：
[base]
name=CentOS-$releasever - Base
baseurl=http://s7repo01/centos/7.2.1511/os/$basearch/
gpgcheck=1
gpgkey=http://s7repo01/centos/RPM-GPG-KEY-CentOS-7
#released updates
[updates]
name=CentOS-$releasever - Updates
baseurl=http://s7repo01/centos/7.2.1511/updates/$basearch/
gpgcheck=1
gpgkey=http://s7repo01/centos/RPM-GPG-KEY-CentOS-7
#additional packages that may be useful
[extras]
name=CentOS-$releasever - Extras
baseurl=http://s7repo01/centos/7.2.1511/extras/$basearch/
gpgcheck=1
gpgkey=http://s7repo01/centos/RPM-GPG-KEY-CentOS-7
#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-$releasever - Plus
baseurl=http://s7repo01/centos/7.2.1511/centosplus/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://s7repo01/centos/RPM-GPG-KEY-CentOS-7
将所有的baseurl属性修改为版本7对应的目录路径，baseurl属性修改后如下：
baseurl=http://s7repo01/centos/7/centosplus/$basearch/
注：只修改版本号即可，对应的仓库地址可能与此不同，能访问则不必修改。
五、继续安装
继续使用如下命令安装：
$ sudo yum -y localinstall docker-engine-selinux-1.13.1-1.el7.centos.noarch.rpm
$ sudo yum -y localinstall docker-engine-1.13.1-1.el7.centos.x86_64.rpm
如果出现某个仓库不能连接的情况，可使用如下命令禁用掉，例（查看具体的错误信息可获知仓库名称，这里是dockerrepo）：
sudo yum-config-manager --disable dockerrepo
重新输入命令，安装成功
附录1：安装中的问题
Loaded plugins: fastestmirror
Repository cloudera-manager is listed more than once in the configuration
Examining docker-engine-selinux-1.13.1-1.el7.centos.noarch.rpm: docker-engine-selinux-1.13.1-1.el7.centos.noarch
Marking docker-engine-selinux-1.13.1-1.el7.centos.noarch.rpm to be installed
Resolving Dependencies
--> Running transaction check
---> Package docker-engine-selinux.noarch 0:1.13.1-1.el7.centos will be installed
--> Processing Dependency: selinux-policy-base >= 3.13.1-102 for package: docker-engine-selinux-1.13.1-1.el7.centos.noarch
http://s7repo01/centos/7.2.1511/os/x86_64/repodata/repomd.xml: [Errno 14] HTTP Error 404 - Not Found
Trying other mirror.
To address this issue please refer to the below knowledge base article
https://access.redhat.com/articles/1320623
If above article doesn't help to resolve this issue please create a bug on https://bugs.centos.org/
http://s7repo01/centos/7.2.1511/extras/x86_64/repodata/repomd.xml: [Errno 14] HTTP Error 404 - Not Found
Trying other mirror.
http://s7repo01/centos/7.2.1511/updates/x86_64/repodata/repomd.xml: [Errno 14] HTTP Error 404 - Not Found
Trying other mirror.
Loading mirror speeds from cached hostfile
... 省略
Error: Package: docker-engine-selinux-1.13.1-1.el7.centos.noarch (/docker-engine-selinux-1.13.1-1.el7.centos.noarch)
Requires: selinux-policy-base >= 3.13.1-102
Installed: selinux-policy-targeted-3.13.1-60.el7.noarch (@anaconda)
selinux-policy-base = 3.13.1-60.el7
Available: selinux-policy-minimum-3.13.1-60.el7.noarch (base)
selinux-policy-base = 3.13.1-60.el7
Available: selinux-policy-minimum-3.13.1-60.el7_2.3.noarch (updates)
selinux-policy-base = 3.13.1-60.el7_2.3
Available: selinux-policy-minimum-3.13.1-60.el7_2.7.noarch (updates)
selinux-policy-base = 3.13.1-60.el7_2.7
Available: selinux-policy-minimum-3.13.1-60.el7_2.9.noarch (updates)
selinux-policy-base = 3.13.1-60.el7_2.9
Available: selinux-policy-mls-3.13.1-60.el7.noarch (base)
selinux-policy-base = 3.13.1-60.el7
Available: selinux-policy-mls-3.13.1-60.el7_2.3.noarch (updates)
selinux-policy-base = 3.13.1-60.el7_2.3
Available: selinux-policy-mls-3.13.1-60.el7_2.7.noarch (updates)
selinux-policy-base = 3.13.1-60.el7_2.7
Available: selinux-policy-mls-3.13.1-60.el7_2.9.noarch (updates)
selinux-policy-base = 3.13.1-60.el7_2.9
Available: selinux-policy-targeted-3.13.1-60.el7_2.3.noarch (updates)
selinux-policy-base = 3.13.1-60.el7_2.3
Available: selinux-policy-targeted-3.13.1-60.el7_2.7.noarch (updates)
selinux-policy-base = 3.13.1-60.el7_2.7
Available: selinux-policy-targeted-3.13.1-60.el7_2.9.noarch (updates)
selinux-policy-base = 3.13.1-60.el7_2.9
Error: Package: docker-engine-selinux-1.13.1-1.el7.centos.noarch (/docker-engine-selinux-1.13.1-1.el7.centos.noarch)
Requires: selinux-policy-targeted >= 3.13.1-102
Installed: selinux-policy-targeted-3.13.1-60.el7.noarch (@anaconda)
selinux-policy-targeted = 3.13.1-60.el7
Available: selinux-policy-targeted-3.13.1-60.el7_2.3.noarch (updates)
selinux-policy-targeted = 3.13.1-60.el7_2.3
Available: selinux-policy-targeted-3.13.1-60.el7_2.7.noarch (updates)
selinux-policy-targeted = 3.13.1-60.el7_2.7
Available: selinux-policy-targeted-3.13.1-60.el7_2.9.noarch (updates)
selinux-policy-targeted = 3.13.1-60.el7_2.9
You could try using --skip-broken to work around the problem
You could try running: rpm -Va --nofiles --nodigest
使用rpm命令安装，可看见需要的依赖包
sudo rpm -ivh docker-engine-selinux-1.13.1-1.el7.centos.noarch.rpm
warning: docker-engine-selinux-1.13.1-1.el7.centos.noarch.rpm: Header V4 RSA/SHA512 Signature,key ID 2c52609d: NOKEY
error: Failed dependencies:
policycoreutils-python is needed by docker-engine-selinux-1.13.1-1.el7.centos.noarch
selinux-policy-base >= 3.13.1-102 is needed by docker-engine-selinux-1.13.1-1.el7.centos.noarch
selinux-policy-targeted >= 3.13.1-102 is needed by docker-engine-selinux-1.13.1-1.el7.centos.noarch
附录2：参考链接
http://www.cnblogs.com/mchina/archive/2013/01/04/2842275.html \
http://www.178linux.com/11404 \
http://www.jianshu.com/p/1fc580b71ea4 \
http://www.jb51.cc/article/p-rmhuylkq-brh.html
