yum报错解决手记
帮别人配置环境，系统是centos 6.5 64位，用yum安装软件时一直报错，前后一共遇到两个错误：
错误1：
[root@localhost yum.repos.d]# yum install telnet
Loaded plugins: fastestmirror, security
Loading mirror speeds from cached hostfile
http://mirror.centos.org/centos/%24releasever/os/x86_64/repodata/repomd.xml: [Errno 14] HTTP Error 404: Not Found
Trying other mirror.
Error: Cannot retrieve repository metadata (repomd.xml) for repository: base. Please verify its path and try again
错误2：
[root@localhost etc]# yum install telnet
Loaded plugins: fastestmirror, security
Determining fastest mirrors
YumRepo Error: All mirror URLs are not using ftp, http[s] or file.
Eg. $releasever is not a valid and current release or hasnt been released yet/
removing mirrorlist with no valid mirrors: /var/cache/yum/base/mirrorlist.txt
Error: Cannot find a valid baseurl for repo: base
服务器的网络和dns是没问题的，yum.repo.d/Centos-Base.repo配置是默认的，其它配置文件不清楚有没有改过。
这两个错误都是和yum的$releasever变量有关，这个变量会读取centos-release包的内容，解决方法是编辑/etc/yum.conf文件，将distroverpkg改为redhat-release或者centos-release即可
vim /etc/yum.conf
distroverpkg=redhat-release
当然，要保证服务器有centos-release包，这个包是随系统安装的，而且一般人不会干掉它
参考文章：