更换镜像源(阿里云/腾讯云)：gpgkey=http://mirrors.tencentyun.com/RPM-GPG-KEY-EPEL-7
baseurl=http://mirrors.tencentyun.com/epel/$releasever/$basearch/
升级Docker后重启容器出现错误(Unknown runtime specified docker-runc)解决方法：
grep -rl 'docker-runc' /var/lib/docker/containers/ | xargs sed -i 's/docker-runc/runc/g'