centos安装 yum

以下是安装yum的步骤：

查看已安装的yum：rpm -qa|grep yum
删除已有的yum：rpm -aq|grep yum|xargs rpm -e --nodeps
下载以下安装包：
wget http://tel.mirrors.163.com/centos/7/os/x86_64/Packages/python-2.7.5-89.el7.x86_64.rpm
wget http://tel.mirrors.163.com/centos/7/os/x86_64/Packages/python-iniparse-0.4-9.el7.noarch.rpm
wget http://tel.mirrors.163.com/centos/7/os/x86_64/Packages/yum-3.4.3-168.el7.centos.noarch.rpm
wget http://tel.mirrors.163.com/centos/7/os/x86_64/Packages/yum-metadata-parser-1.1.4-10.el7.x86_64.rpm
wget http://tel.mirrors.163.com/centos/7/os/x86_64/Packages/yum-plugin-fastestmirror-1.1.31-54.el7_8.noarch.rpm
安装：
rpm -ivh python-2.7.5-89.el7.x86_64.rpm python-iniparse-0.4-9.el7.noarch.rpm --nodeps --force
rpm -ivh yum-metadata-parser-1.1.4-10.el7.x86_64.rpm --nodeps --force
rpm -ivh yum-3.4.3-168.el7.centos.noarch.rpm yum-plugin-fastestmirror-1.1.31-54.el7_8.noarch.rpm --nodeps --force
更改yum源：
首先备份/etc/yum.repos.d/CentOS-Base.repo：mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup