购买的云服务器运行yum命令出现yum command not found。
通过将云主机自带的yum和python卸载掉，并且同时需要关注/usr/bin/yum文件的首行解释。我定义其为"#!/usr/bin/python"
1.卸载python:
1 rpm -qa|grep python|xargs rpm -e --allmatches --nodeps 2 whereis python|xargs rm -fr
2.卸载yum:
1 rpm -qa|grep yum|xargs rpm -e --allmatches --nodeps 2 rm -rf /etc/yum.repos.d/* 3 whereis yum|xargs rm -fr
3.创建目录python和yum用以存放rpm包：
1 mkdir /usr/local/src/python
2 mkdir /usr/local/src/yum
4.使用wget分别下载python以及yum的rpm包（注意：一定要和系统的版本号对应）
（1）下载python的rpm包：
1 #cd /usr/local/src/python 进入目录 2 3 #wget http://vault.centos.org/7.2.1511/os/x86_64/Packages/python-2.7.5-34.el7.x86_64.rpm 4 #wget http://vault.centos.org/7.2.1511/os/x86_64/Packages/python-iniparse-0.4-9.el7.noarch.rpm 5 #wget http://vault.centos.org/7.2.1511/os/x86_64/Packages/python-pycurl-7.19.0-17.el7.x86_64.rpm 6 #wget http://vault.centos.org/7.2.1511/os/x86_64/Packages/python-devel-2.7.5-34.el7.x86_64.rpm 7 #wget http://vault.centos.org/7.2.1511/os/x86_64/Packages/python-libs-2.7.5-34.el7.x86_64.rpm 8 #wget http://vault.centos.org/7.2.1511/os/x86_64/Packages/python-urlgrabber-3.10-7.el7.noarch.rpm 9 #wget http://vault.centos.org/7.2.1511/os/x86_64/Packages/rpm-python-4.11.3-17.el7.x86_64.rpm
（2）下载yum的rpm包：
1 #cd /usr/local/src/yum 2 3 #wget http://vault.centos.org/7.2.1511/os/x86_64/Packages/yum-3.4.3-132.el7.centos.0.1.noarch.rpm 4 #wget http://vault.centos.org/7.2.1511/os/x86_64/Packages/yum-metadata-parser-1.1.4-10.el7.x86_64.rpm 5 #wget http://vault.centos.org/7.2.1511/os/x86_64/Packages/yum-plugin-fastestmirror-1.1.31-34.el7.noarch.rpm
5.安装python以及yum的rpm包
（1）安装python:
1 #cd /usr/local/src/python 2 3 #rpm -ivh python-* rpm-python-* 4 出现安装包的依赖问题，此时如下解决即可： 5 6 #rpm -ivh python-* rpm-python-* --nodeps --force 7 --nodeps --force为不考虑依赖包，强制安装。 8 9 安装完后即可运行python:
（2）安装yum:
1 #cd /usr/local/src/yum 2 #rpm -ivh yum-*
