yum源中$releasever不能被系統識別

服務器yum操作報錯

http://mirrors.cloud.aliyuncs.com/centos/%24releasever/os/x86_64/repodata/repomd.xml: [Errno 14] HTTP Error 404 - Not Found

$releasever變量沒有被系統識別，查看rpm -q centos-release，結果package centos-release is not installed，此包沒有安裝。

解決方法：

1. 修改/etc/yum.repos.d/CentOS-Base.repo中$releasever爲對應的系統版本路徑，比如centos7就改爲7

   如：

   [base]
   name=CentOS-7
   enabled=1
   failovermethod=priority
   baseurl=http://mirrors.cloud.aliyuncs.com/centos/7/os/$basearch/
   gpgcheck=1
   gpgkey=http://mirrors.cloud.aliyuncs.com/centos/RPM-GPG-KEY-CentOS-7
   
   [updates]
   name=CentOS-7
   enabled=1
   failovermethod=priority
   baseurl=http://mirrors.cloud.aliyuncs.com/centos/7/updates/$basearch/
   gpgcheck=1
   gpgkey=http://mirrors.cloud.aliyuncs.com/centos/RPM-GPG-KEY-CentOS-7
   
   [extras]
   name=CentOS-7
   enabled=1
   failovermethod=priority
   baseurl=http://mirrors.cloud.aliyuncs.com/centos/7/extras/$basearch/
   gpgcheck=1
   gpgkey=http://mirrors.cloud.aliyuncs.com/centos/RPM-GPG-KEY-CentOS-7
   
   

   2.安裝 yum install centos-release，在/etc/yum.repos.d生成了新的源文件CentOS-Base.repo.rpmnew，修改覆蓋之前的文件mv CentOS-Base.repo.rpmnew CentOS-Base.repo，$releasever就可以正常解析了。

番外：

查看系統版本命令：

lsb_release -a

vim全局替換命令:

:%s/$releaserver/7/g

:{作用範圍}s/{目標}/{替換}/{替換標誌}

參考：

vim https://harttle.land/2016/08/08/vim-search-in-file.html

系統版本 https://www.qiancheng.me/post/coding/show-linux-issue-version

yum https://www.jianshu.com/p/925960eaeb21