最近在虚拟机下面安装了个CentOS 5.5，使用yum更新时发现下载速度异常慢。可以修改yum的配置文件，把其镜像指向国内的服务器即可。
方案一：
# cd /etc/yum.repos.d/
# mv CentOS-Base.repo CentOS-Base.repo.bak
# wget http://docs.linuxtone.org/soft/lemp/CentOS-Base.repo
cyc_edwin方法
[root@localhost ~]# cd /etc/yum.repos.d/
[root@localhost ~]# mv ./CentOS-Base.repo ./CentOS-Base.repo.bak
[root@localhost ~]# wget http://mirrors.163.com/.help/CentOS-Base-163.repo
[root@localhost ~]# mv CentOS-Base-163.repo CentOS-Base.repo
方案二：
手段修改CentOS-Base.repo文件，将baseurl设置成baseurl=http://ftp.sjtu.edu.cn/centos/5/addons/$basearch/
详细配置如下：
[base]
name=CentOS-5-Base
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever5&arch=$basearch&repo=os
#baseurl=http://mirror.centos.org/centos/$releasever/os/$basearch/
baseurl=http://ftp.sjtu.edu.cn/centos/5/os/$basearch/
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos5
#released updates
[update]
name=CentOS-5-Updates
#mirrorlist=http://mirrorlist.centos.org/?release=4&arch=$basearch&repo=updates
baseurl=http://ftp.sjtu.edu.cn/centos/5/updates/$basearch/
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos5
#packages used/produced in the build but not released
[addons]
name=CentOS-5-Addons
#mirrorlist=http://mirrorlist.centos.org/?release=4&arch=$basearch&repo=addons
baseurl=http://ftp.sjtu.edu.cn/centos/5/addons/$basearch/
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos5
#additional packages that may be useful
[extras]
name=CentOS-5-Extras
#mirrorlist=http://mirrorlist.centos.org/?release=4&arch=$basearch&repo=extras
baseurl=http://ftp.sjtu.edu.cn/centos/5/extras/$basearch/
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos5
#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-5-Plus
#mirrorlist=http://mirrorlist.centos.org/?release=4&arch=$basearch&repo=centosplus
baseurl=http://ftp.sjtu.edu.cn/centos/5/centosplus/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos5
#contrib – packages by Centos Users
[contrib]
name=CentOS-5-Contrib
#mirrorlist=http://mirrorlist.centos.org/?release=4&arch=$basearch&repo=contrib
baseurl=http://ftp.sjtu.edu.cn/centos/5/contrib/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos5
##############################################################
导入 key
＃ rpm –import http://ftp.sjtu.edu.cn/centos/5/os/i386/RPM-GPG-KEY-CentOS-5
运行，测试
＃ yum update
全部删除临时文件
#yum clean all
