yum 讀取不到系統版本

[root@SRV54 yum.repos.d]# yum install libnuma* glibc*
Loaded plugins: fastestmirror, security
Loading mirror speeds from cached hostfile
YumRepo Error: All mirror URLs are not using ftp, http[s] or file.
Eg. $releasever is not a valid and current release or hasnt been released yet/
removing mirrorlist with no valid mirrors: /var/cache/yum/i386/$releasever/base/mirrorlist.txt
Error: Cannot find a valid baseurl for repo: base

google 解決方法大部分都是因為無法解析網址、需要修改 /ect/resolv.conf
但是這邊是無法取得正確的 $releasever 變數
因此手動將 /etc/yum.repos.d/CentOS-Base.repo 裡面的 $releasever 改成 6 就好了（我的版本是6.5）

●vi /etc/yum.repos.d/CentOS-Base.repo
:%s/$releasever/6/g

參考文章：YumRepo Error: All mirror URLs are not using 問題解決