CentOS系统yum源使用报错：Error: Cannot retrieve repository metadata (repomd.xml) for repository: rpmforge.
服务器上的yum突然不好使用，使用yum的时候报错如下：
[root@bastion-IDC src]# yum list
......
Could not retrieve mirrorlist http://mirrorlist.repoforge.org/el6/mirrors-rpmforge error was
14: PYCURL ERROR 7 - "couldn't connect to host"
http://apt.sw.be/redhat/el6/en/x86_64/rpmforge/repodata/repomd.xml: [Errno 14]
PYCURL ERROR 7 - "couldn't connect to host"
Trying other mirror.
Error: Cannot retrieve repository metadata (repomd.xml) for repository: rpmforge.
Please verify its path and try again
解决办法：（或者把/etc/yum.repos.d下的文件全部删除，然后将能正常使用yum的同类服务器的这个目录下的文件全部拷贝过来，然后yum clean all 和yum makecache 即可）
***新的CentOS-Base.repo 到/etc/yum.repos.d/
[root@bastion-IDC src]# cd /etc/yum.repos.d/
其实就是将yum源更改为阿里云的yum源,***作如下：
1）centos5.*的***连接：
[root@bastion-IDC yum.repos.d]# wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-5.repo
2）centos6.*的***连接：
[root@bastion-IDC yum.repos.d]# wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-6.repo
3）centos7.*的***连接：
[root@bastion-IDC yum.repos.d]# wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
然后执行以下命令：
[root@bastion-IDC yum.repos.d]# rpm -e rpmforge-release --nodeps
-------------------------------------------------------------------------------------------------------------
如果报错：
error: package rpmforge-release is not installed
解决办法：安装这个源
***地址：https://pan.baidu.com/s/1pKBtm11
提取密码：erte
[root@bastion-IDC yum.repos.d]# rpm -ivh rpmforge-release-0.5.2-2.el6.rf.x86_64.rpm
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[root@bastion-IDC yum.repos.d]# yum clean all
[root@bastion-IDC yum.repos.d]# yum makecache
//将服务器上的软件包信息缓存到本地,以提高搜索安装软件的速度
[root@bastion-IDC yum.repos.d]# yum update
//最后再次使用yum就ok了
[root@bastion-IDC yum.repos.d]# yum list
