centos自带的dvd中的官方base源，丢失了可以复制下面的内容

/etc/yum.repos.d/CentOS-Base.repo
文件中的内容，同样适用于centos6

[base]
name=CentOS-$releasever - Base
mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os
#baseurl=http://mirror.centos.org/centos/$releasever/os/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5