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
本文转自 linuxpp 51CTO博客，原文链接：http://blog.51cto.com/1439337369/1714354，如需转载请自行联系原作者
