查看yum的源文件CentOS-Base.repo的内容

你可以按照以下步骤查看CentOS-Base.repo的内容：

1. 打开终端，并以root用户身份登录系统。
2. 运行以下命令打开CentOS-Base.repo文件：

   vi /etc/yum.repos.d/CentOS-Base.repo

该命令将使用vi编辑器打开CentOS-Base.repo文件。

3. 按下"i"键进入编辑模式，此时你可以编辑文件内容。
4. 查看文件内容，CentOS-Base.repo文件中应该包含如下内容：

   [base]
   name=CentOS-$releasever - Base
   mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os&infra=$infra
   #baseurl=http://mirror.centos.org/$contentdir/$releasever/Base/$basearch/os/
   gpgcheck=1
   gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7

   #released updates
   [updates]
   name=CentOS-$releasever - Updates
   mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=updates&infra=$infra
   #baseurl=http://mirror.centos.org/$contentdir/$releasever/updates/$basearch/
   gpgcheck=1
   gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7

   #additional packages that may be useful
   [extras]
   name=CentOS-$releasever - Extras
   mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=extras&infra=$infra
   #baseurl=http://mirror.centos.org/$contentdir/$releasever/extras/$basearch/
   gpgcheck=1
   gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7

   #additional packages that extend functionality of existing packages
   [centosplus]
   name=CentOS-$releasever - Plus
   mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=centosplus&infra=$infra
   #baseurl=http://mirror.centos.org/$contentdir/$releasever/centosplus/$basearch/
   gpgcheck=1
   enabled=0
   gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7

   #contrib - packages by Centos Users
   [contrib]
   name=CentOS-$releasever - Contrib
   mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=contrib&infra=$infra
   #baseurl=http://mirror.centos.org/$contentdir/$releasever/contrib/$basearch/
   gpgcheck=1
   enabled=0
   gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7

5. 按下"Esc"键退出编辑模式，然后输入":wq"保存并退出文件。

通过以上步骤，你可以查看CentOS-Base.repo文件的内容。注意，该文件中包含了CentOS系统默认的yum源配置信息。