安裝yum：
最近在centos7上安裝了python3導致yum不能用，被其他人卸載掉后重新安裝
#下載yum安裝包
wget http://mirrors.163.com/centos/6/os/x86_64/Packages/yum-3.2.27-14.el6.centos.noarch.rpm
wget http://mirrors.163.com/centos/7/os/x86_64/Packages/python-iniparse-0.4-9.el7.noarch.rpm
wget http://mirrors.163.com/centos/7/os/x86_64/Packages/yum-metadata-parser-1.1.4-10.el7.x86_64.rpm
wget http://mirrors.163.com/centos/7/os/x86_64/Packages/yum-3.4.3-158.el7.centos.noarch.rpm
wget http://mirrors.163.com/centos/7/os/x86_64/Packages/yum-plugin-fastestmirror-1.1.31-45.el7.noarch.rpm
#安裝
rpm -ivh python-iniparse-0.4-9.el7.noarch.
rpm -ivh yum-metadata-parser-1.1.4-10.el7.x86_64.rpm
rpm -ivh yum-3.4.3-158.el7.centos.noarch.rpm #會出現問題1
wget http://mirrors.163.com/centos/7/os/x86_64/Packages/rpm-4.11.3-32.el7.x86_64.rpm
rpm -Uvh rpm-4.11.3-32.el7.x86_64.rpm --nodeps
rpm -ivh yum-3.4.3-158.el7.centos.noarch.rpm yum-plugin-fastestmirror-1.1.31-45.el7.noarch.rpm
錯誤：依賴檢測失敗：
rpm >= 0:4.11.3-22 被 yum-3.4.3-154.el7.centos.noarch 需要
yum >= 3.0 被 yum-plugin-fastestmirror-1.1.31-45.el7.noarch 需要
解決：
wget http://mirrors.163.com/centos/7/os/x86_64/Packages/rpm-4.11.3-32.el7.x86_64.rpm
rpm -Uvh rpm-4.11.3-32.el7.x86_64.rpm --nodeps
成功！
注意：升級成了python3也可以用python2,
因為yum使用python2，因此替換為python3后可能無法正常工作，繼續使用這個python2.7. 因此修改yum配置文件
sudo vim /usr/bin/yum
把文件頭部的#!/usr/bin/python改成#!/usr/bin/python2.7保存退出即可.
/usr/libexec/urlgrabber-ext-down看看，發下他也使用了/usr/bin/python，於是跟前面一樣，改為2.7，完成。
轉載請說明出處，謝謝！本文地址：https://www.cnblogs.com/ontoweb-zp/p/9268008.html