更改Centos的更新源

我的系统是6.3

1．修改/etc/yum.repos.d/CentOS-Base.repo为: 
[base] 
name=CentOS-5-Base 
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever5&arch=$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．校验Key导入：执行 
rpm --import http://ftp.sjtu.edu.cn/centos/5.3/os/i386/RPM-GPG-KEY-CentOS-5 
3．进行升级：执行 
yum update 
Ok了，搞定。