Change the update source for CentOS

My system is 6.3.

1. Modify the/etc/yum.repos.d/centos-base.repo to: 
[Base] 
Name=centos-5-base 
#mirrorlist =http://mirrorlist.centos.org/?release= $releasever 5&arch= $basearch & 
Repo=os 
#baseurl =http://mirror.centos.org/centos/$releasever/os/$basearch/ 
baseurl=http://ftp.sjtu.edu.cn/centos/5.3/os/$basearch/ 
Gpgcheck=1 
Gpgkey=http://mirror.centos.org/centos/rpm-gpg-key-centos5 
#releasedupdates 
[UPDATE] 
Name=centos-5-updates 
#mirrorlist =http://mirrorlist.centos.org/?release=4&arch= $basearch &repo=updates 
baseurl=http://ftp.sjtu.edu.cn/centos/5.3/updates/$basearch/ 
Gpgcheck=1 
Gpgkey=http://mirror.centos.org/centos/rpm-gpg-key-centos5 
#packagesused/producedinthebuildbutnotreleased 
[Addons] 
Name=centos-5-addons 
#mirrorlist =http://mirrorlist.centos.org/?release=4&arch= $basearch &repo=addons 
baseurl=http://ftp.sjtu.edu.cn/centos/5.3/addons/$basearch/ 
Gpgcheck=1 
Gpgkey=http://mirror.centos.org/centos/rpm-gpg-key-centos5 
#additionalpackagesthatmaybeuseful 
[Extras] 
Name=centos-5-extras 
#mirrorlist =http://mirrorlist.centos.org/?release=4&arch= $basearch &repo=extras 
baseurl=http://ftp.sjtu.edu.cn/centos/5.3/extras/$basearch/ 
Gpgcheck=1 
Gpgkey=http://mirror.centos.org/centos/rpm-gpg-key-centos5 
#additionalpackagesthatextendfunctionalityofexistingpackages 
[Centosplus] 
Name=centos-5-plus 
#mirrorlist =http://mirrorlist.centos.org/?release=4&arch= $basearch &repo=centosplus 
baseurl=http://ftp.sjtu.edu.cn/centos/5.3/centosplus/$basearch/ 
Gpgcheck=1 
Enabled=0 
Gpgkey=http://mirror.centos.org/centos/rpm-gpg-key-centos5 
#contrib-packagesbycentosusers 
[Contrib] 
Name=centos-5-contrib 
#mirrorlist =http://mirrorlist.centos.org/?release=4&arch= $basearch &repo=contrib 
baseurl=http://ftp.sjtu.edu.cn/centos/5.3/contrib/$basearch/ 
Gpgcheck=1 
Enabled=0 
Gpgkey=http://mirror.centos.org/centos/rpm-gpg-key-centos5 
2. Verify key import: Execute 
RPM--import http://ftp.sjtu.edu.cn/centos/5.3/os/i386/RPM-GPG-KEY-CentOS-5 
3. To upgrade: Execute 
Yum Update 
OK, it's done.

This article is from the "ZPP" blog, make sure to keep this source http://1439337369.blog.51cto.com/10270624/1714354

Change the update source for CentOS