今天给一台服务器上的服务扩容，添加软连接，顺便打算把原来二进制启动的docker重新用yum的方法安装一遍，但还是遇到了以前遇到过的错误，一开始是各种
乱七八糟的rpm过低，无法升级，于是手动加载了一遍：
rpm -Uvh selinux-policy-3.13.1-102.el7.noarch.rpm libsemanage-2.5-4.el7.x86_64.rpm policycoreutils-2.5-8.el7.x86_64.rpm selinux-policy-targeted-3.13.1-102.el7.noarch.rpm libsemanage-python-2.5-4.el7.x86_64.rpm libselinux-utils-2.5-6.el7.x86_64.rpm policycoreutils-2.5-8.el7.x86_64.rpm policycoreutils-python-2.5-8.el7.x86_64.rpm libselinux-2.5-6.el7.x86_64.rpm libselinux-python-2.5-6.el7.x86_64.rpm setools-libs-3.3.8-1.1.el7.x86_64.rpm
完成后还是报错：
大致意思是从https://get.daocloud.io/docker/yum-repo/main/centos/7/Packages/docker-engine-1.13.1-1.el7.centos.x86_64.rpm无法下载，因为客户的环境隔离的比较严格，可能跟代理设置有关系，导致了这种奇葩问题
于是乎尝试手动下载，结果可以，直接
wget https://get.daocloud.io/docker/yum-repo/main/centos/7/Packages/docker-engine-1.13.1-1.el7.centos.x86_64.rpm
wget https://get.daocloud.io/docker/yum-repo/main/centos/7/Packages/docker-engine-selinux-1.13.1-1.el7.centos.x86_64.rpm
rpm -ivh docker-engine-1.13.1-1.el7.centos.x86_64.rpm docker-engine-selinux-1.13.1-1.el7.centos.x86_64.rpm
安装成功，再次执行
curl -sSL https://get.daocloud.io/docker | sh
docker安装成功
软连接：ln -s /midware/docker /var/lib/docker
ln -s /midware/workspace /home/hudson/workspace
其中/home/hudson/workspace 没有io权限，需要
chown hudson workspace/
chgrp hudson workspace