yum配置文件变量详解

yun源配置路径：/etc/yum.repos.d/xxx.repo

先看下yun配置文件的内容

[root@py git]# cat /etc/yum.repos.d/epel.repo 
[epel]
name=Extra Packages for Enterprise Linux 6 - $basearch
#baseurl=http://download.fedoraproject.org/pub/epel/6/$basearch
mirrorlist=https://mirrors.fedoraproject.org/metalink?repo=epel-6&arch=$basearch
failovermethod=priority
enabled=1
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-6

可以看到 里面有几个变量 $basearch $arch等

其实最好的资料就是man手册 这些变量内容 我们可以在man手册里面找到 

>> man yum.conf

VARIABLES
       There  are  a  number  of variables you can use to ease maintenance of yum’s configuration files.
       They are available in the values of several options including name, baseurl and commands.

              $releasever This will be replaced with the value of the version of the package  listed  in
              distroverpkg. This defaults to the version of ‘redhat-release’ package.

              $arch This will be replaced with the architecture or your system as detected by yum.

              $basearch  This  will be replaced with your base architecture in yum. For example, if your
              $arch is i686 your $basearch will be i386.

              $uuid This will be replaced with a unique but persistent uuid for this machine.  The value
              that  is first generated will be stored in /var/lib/yum/uuid and reused until this file is
              deleted.

              $YUM0-$YUM9 These will be replaced with the value of the shell environment variable of the
              same  name.  If  the shell environment variable does not exist then the configuration file
              variable will not be replaced.

这里可以看到 $releasever的值来自distroverpkg 那么distroverpkg是什么呢? 我们继续在man yum.conf里面查找可以看到

distroverpkg The package used by yum to determine the "version" of the distribution.  This
              can  be any installed package. Default is ‘redhat-release’. You can see what provides this
              manually by using: "yum whatprovides redhat-release".

$arch 是系统架构 执行执行arch命令查看

[root@py git]# arch 
x86_64

$basearch 这将被你yum所在系统的基础架构所取代 

例如 如果您的$ arch是i686 你的$ basearch将是i386

$YUM0 - $YUM9 用户自定义变量

这些将被替换为相同名称的shell环境变量的值 如果shell环境变量不存在 那么配置文件变量将不会被替换

这里有个简单的Python命令可以查看这些值

[root@py git]# /usr/bin/python -c 'import yum, pprint; yb = yum.YumBase(); pprint.pprint(yb.conf.yumvar, width=1)'
Loaded plugins: fastestmirror
{'arch': 'ia32e',
 'basearch': 'x86_64',
 'infra': 'stock',
 'releasever': '6',
 'uuid': 'e51c4e78-7b06-473c-8605-1c998de5a792'}