1）配置源代码的源
在CentOS中，源的配置文件为：/etc/yum.repos.d/CentOS-Base.repo，修改该文件需要root权限。
打开该文件，查看该文件的内容，在本人的机子上，该文件的内容如下：
# CentOS-Base.repo## The mirror system uses the connecting IP address of the client and the# update status of each mirror to pick mirrors that are updated to and# geographically close to the client. You should use this for CentOS updates# unless you are manually picking other mirrors.## If the mirrorlist= does not work for you, as a fall back you can try the # remarked out baseurl= line instead.##[base]name=CentOS-$releasever – Basemirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os#baseurl=http://mirror.centos.org/centos/$releasever/os/$basearch/gpgcheck=1gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6#released updates [updates]name=CentOS-$releasever – Updatesmirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=updates#baseurl=http://mirror.centos.org/centos/$releasever/updates/$basearch/gpgcheck=1gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6#additional packages that may be useful[extras]name=CentOS-$releasever – Extrasmirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=extras#baseurl=http://mirror.centos.org/centos/$releasever/extras/$basearch/gpgcheck=1gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6#additional packages that extend functionality of existing packages[centosplus]name=CentOS-$releasever – Plusmirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=centosplus#baseurl=http://mirror.centos.org/centos/$releasever/centosplus/$basearch/gpgcheck=1enabled=0gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6#contrib – packages by Centos Users[contrib]name=CentOS-$releasever – Contribmirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=contrib#baseurl=http://mirror.centos.org/centos/$releasever/contrib/$basearch/gpgcheck=1enabled=0gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6
该文件中有两个变量：releasever和basearch，分别表示release版本和分支，如本人的机子上，这两个值分别为6和i386。注意，releasever并不会细分为次级版本，即不会是6.6之类的。
从该文件的内容可以知道，该文件共有5个节，也就是说本人的机子的软件来源有5处，分别为base、updates、extras、centosplus和contrib。所以只需要为如下的5处软件源指定其源代码的源即可。在文件的末尾加上如下的内容：
[base-src]name=CentOS-$releasever – Base srcbaseurl=http://vault.centos.org/6.6/os/Source/gpgcheck=1gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6[updates-src]name=CentOS-$releasever – Updates src-centosbaseurl=http://vault.centos.org/6.6/updates/Source/gpgcheck=1gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6[extras-src]name=CentOS-$releasever – Extras src-centosbaseurl=http://vault.centos.org/6.6/extras/Source/gpgcheck=1gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6[centosplus-src]name=CentOS-$releasever – Plus src-centosbaseurl=http://vault.centos.org/6.6/centosplus/Source/gpgcheck=1gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6[contrib-src]name=CentOS-$releasever – Contrib src-centosbaseurl=http://vault.centos.org/6.6/contrib/Soruce/gpgcheck=1gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6
由于不同的版本设置会有所不同，所以其设置会有所不同，方法可总结为如下：
（1）gpgkey与该文件中已有的节的gpgkey相同
（2）为了确认文件的存在和情况，可以打开网站查看具体的情况，再根据具体的情况来填写
（3）设置baseurl时需要根据自己的系统的版本来设置，，如本人的机子为CentOS-6.6，则在设置时，相关的参数就设置为6.6，即后接的子路径为6.6。
该文件的作用是为yum其及相关工作的下载提供一个源，如在使用yumdownloader（下面会讲到）下载源代码时，会发生如下动作：
（1）下载$baseurl/repodata/repomd.xml文件，若该repomd.xml文件比系统中的新，更新系统中的相应的repomd.xml
（2）下载$baseurl/SPackages/中的相应的源代码rpm包。
2）使用which命令查看ls命令的位置，如下：
which ls
# 输出：/bin/ls
3）使用rpm命令查询ls命令所属的包，如下：
谦受益，满招损。
