定义yum超时时间：

vi /etc/yum.conf

timeout=120

修改源：（全部复制粘贴即可）

cd /etc/yum.repos.d/

mv rhel-debuginfo.repo rhel-debuginfo.repo.bak

wget http://www.yodav.com/project/centos/yum/rpmforge.repo

wget http://www.yodav.com/project/centos/yum/mirrors-rpmforge

wget http://www.yodav.com/project/centos/yum/dag.repo

wget http://www.yodav.com/project/centos/yum/rhel-debuginfo.repo

rpm --import http://mirror.leaseweb.com/centos/RPM-GPG-KEY-CentOS-5

cd /tmp

wget http://packages.sw.be/rpmforge-release/rpmforge-release-0.5.1-1.el5.rf.x86_64.rpm

rpm -ivh rpmforge-release-0.5.1-1.el5.rf.x86_64.rpm

yum install yum-fastestmirror