[repositoryID] #具有唯一性 name=some name for this repository baseurl=url://path/to/repository #yum repository的url可以为多个，路径下必须有repodata enable=1 #是否开启，1为开启，0为关闭，不写的话，默认开启 gpgckeck=1 gpgkey=URL cost=1000 enablegroup=1 #是否允许使用包组，默认是允许
但是我们可以看到CentOS-Base.repo里面没有baseurl而是mirrorlist，mirrorlist指向的URL就是存放了baseurl的位置。
yum的repo配置文件中的可用的变量：
$releasever:当前os的发行版的主版本号 $arch：平台 $basearch：基础平台 $YUM0-$YUM9：用户自定义的变量
yum命令的用法
yum [options] [command] [package ...] command is one of: * install package1 [package2] [...] * update [package1] [package2] [...] * update-to [package1] [package2] [...] * update-minimal [package1] [package2] [...] * check-update * upgrade [package1] [package2] [...] * upgrade-to [package1] [package2] [...] * distribution-synchronization [package1] [package2] [...] * remove | erase package1 [package2] [...] * autoremove [package1] [...] * list [...] * info [...] * provides | whatprovides feature1 [feature2] [...] * clean [ packages | metadata | expire-cache | rpmdb | plugins | all ] * makecache [fast] * groups [...] * search string1 [string2] [...] * shell [filename] * resolvedep dep1 [dep2] [...] (maintained for legacy reasons only - use repoquery or yum provides) * localinstall rpmfile1 [rpmfile2] [...] (maintained for legacy reasons only - use install) * localupdate rpmfile1 [rpmfile2] [...] (maintained for legacy reasons only - use update) * reinstall package1 [package2] [...] * downgrade package1 [package2] [...] * deplist package1 [package2] [...] * repolist [all|enabled|disabled] * repoinfo [all|enabled|disabled] * repository-packages <enabled-repoid> <install|remove|remove-or-reinstall|remove-or-
yum命令1.显示repository列表：
repolist [all|enabled|disabled] all：显示所有的yum repository enable：不带参数默认显示启用的yum repository disable：显示关闭的yum repository