centos7 yum install timeout

https://yum.dockerproject.org/repo/main/centos/7/repodata/repomd.xml: [Errno 12] Timeout on https://yum.dockerproject.org/repo/main/centos/7/repodata/repomd.xml: (28, 'Operation timed out after 30001 milliseconds with 0 out of 0 bytes received')
正在尝试其它镜像。

#  我遇到的主要是上述错误

### 备份这个文件修改$relasever 为7.2.1511

sed -i 's/$releasever/7.2.1511/g' /etc/yum.repos.d/CentOS-Sources.repo

yum clean all