Yum出錯Error: Cannot find a valid baseurl for repo: addons

centos yum 錯誤 Error: Cannot find a valid baseurl for repo: addons 裝了個CentOS 5.x,使用yum時出現了下面的錯誤提示。
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
Could not retrieve mirrorlist http://mirrorlist.centos.org/?release=5&arch=i386&repo=addons error was
[Errno 4] IOError: <urlopen error (-3, ‘Temporary failure in name resolution’)>
Error: Cannot find a valid baseurl for repo: addons
然後 ping mirrorlist.centos.org 發現ping不通。懷疑是dns設置問題。 ping www.ctohome.com 也出現 unknown host www.ctohome.com 的錯誤。多試一試偶爾會ping通，說明dns的確有問題。於是，我們來修改dns配置：
echo “nameserver 8.8.8.8″ >> /etc/resolv.conf
再次yum，成功。