一、本地yum源
1、系统默认已经安装了可使用yum的软件包，所以可以直接配置：
[root@localhost ~]# cd /etc/yum.repos.d/ yum源配置文件放置目录
[root@localhost yum.repos.d]# mv CentOS-Base.repo CentOS-Base.repo.bak 先将网络yum源配置文件更名（让其失效）
[root@localhost yum.repos.d]# vim CentOS-Media.repo 编辑本地yum源文件
[c6-media]
name=CentOS-$releasever - Media 本地yum源名称（可随意修改）
baseurl=file:///mnt/sr0 光盘挂载目录/mnt/sr0
gpgcheck=1
enabled=1 使用此yum源（等于0为不启用）
gpgkey=file:///mnt/sr0/RPM-GPG-KEY-CentOS-6 本地yum源密钥
二、网络yum源
（前提是必须能连上互联网，此处使用的yum源是中国科技大学的地址如下：
中国科技大学：http://centos.ustc.edu.cn/centos/）
[root@localhost yum.repos.d]# mv CentOS-Base.bak CentOS-Base.repo 如果之前没更名就不用操作此步骤
[root@localhost yum.repos.d]# vim CentOS-Base.repo 编辑网络yum源文件
[base]
name=CentOS-$releasever - Base
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os
baseurl=http://centos.ustc.edu.cn/centos/$releasever/os/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6
#released updates
[updates]
name=CentOS-$releasever - Updates
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=updates
baseurl=http://centos.ustc.edu.cn/centos/$releasever/updates/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6
#additional packages that may be useful
[extras]
name=CentOS-$releasever - Extras
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=extras
baseurl=http://centos.ustc.edu.cn/centos/$releasever/extras/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6
#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-$releasever - Plus
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=centosplus
baseurl=http://centos.ustc.edu.cn/centos/$releasever/centosplus/$basearch/
gpgcheck=1
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6
#contrib - packages by Centos Users
[contrib]
name=CentOS-$releasever - Contrib
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=contrib
baseurl=http://centos.ustc.edu.cn/centos/$releasever/contrib/$basearch/
gpgcheck=1
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6
三、注意事项：
使用yum时最好只能让一个yum源生效，因为系统默认优先使用网络yum源。