事件的起因：安装了anaconda，环境总是用到/usr/bin/python，就把python删了，哪知道之后yum就不能用了

• 教训：通过合理配置环境变量使用python3，系统自带的python万万不能删
• 修复的前提：确认rpm命令可用

首先删除系统中所有的python和yum残余

参考博客

# 卸载python
rpm -qa|grep python|xargs rpm -ev --allmatches --nodeps 
whereis python |xargs rm -frv   
whereis python  # 确认删干净了
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# 卸载yum
rpm -qa|grep yum|xargs rpm -ev --allmatches --nodeps 
whereis yum |xargs rm -frv 
whereis yum # 确认删干净了
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这个过程中，anaconda中的python也被删掉了…其实应该可以通过环境变量设置不删掉，但是还是删了，所以anaconda之后又要重装

通过Centos官网下载rpm安装包修复

参考博客2

查看系统版本号和架构

lsb_release -a  # 查看系统版本号 Centos 7.9.2009
uname -m  # 查看服务器架构  x86_64
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找到官网对应的rpm包并下载

我的系统对应的网址

下载这些包

popt-devel-1.13-16.el7.x86_64.rpm
python-2.7.5-89.el7.x86_64.rpm
python2-rpm-macros-3-34.el7.noarch.rpm
python-backports-1.0-8.el7.x86_64.rpm
python-backports-ssl_match_hostname-3.5.0.1-1.el7.noarch.rpm
python-chardet-2.2.1-3.el7.noarch.rpm
python-devel-2.7.5-89.el7.x86_64.rpm
python-iniparse-0.4-9.el7.noarch.rpm
python-ipaddress-1.0.16-2.el7.noarch.rpm
python-kitchen-1.1.1-5.el7.noarch.rpm
python-libs-2.7.5-89.el7.x86_64.rpm
python-pycurl-7.19.0-19.el7.x86_64.rpm
python-rpm-macros-3-34.el7.noarch.rpm
python-setuptools-0.9.8-7.el7.noarch.rpm
python-srpm-macros-3-34.el7.noarch.rpm
python-urlgrabber-3.10-10.el7.noarch.rpm
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修复python

rpm -ivh python*.rpm
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修复成功

修复yum

首先要安装rpm-python

rpm -ivh rpm-python-4.11.3-45.el7.x86_64.rpm
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报错

error: Failed dependencies:
        rpm = 4.11.3-45.el7 is needed by rpm-python-4.11.3-45.el7.x86_64
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查看系统安装的rpm版本号rpm -qa|grep rpm

由于我的rpm升级过，本来应该是rpm-4.11.3-45.el7版本，但现在变成了
rpm-4.11.3-48.el7_9.x86_64，所以rpm-python-4.11.3-45.el7.x86_64.rpm无法安装的

到updates下面去找这个rpm包，网址

果然找到了

安装

rpm -ivh rpm-python-4.11.3-48.el7_9.x86_64.rpm

Preparing...                          ################################# [100%]
Updating / installing...
   1:rpm-python-4.11.3-48.el7_9       ################################# [100%]
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这就装好了
下载这些包

yum-3.4.3-168.el7.centos.noarch.rpm
yum-metadata-parser-1.1.4-10.el7.x86_64.rpm
yum-plugin-aliases-1.1.31-54.el7_8.noarch.rpm
yum-plugin-fastestmirror-1.1.31-54.el7_8.noarch.rpm
yum-plugin-protectbase-1.1.31-54.el7_8.noarch.rpm
yum-utils-1.1.31-54.el7_8.noarch.rpm
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rpm -ivh yum*.rpm报错，依赖没有装好

libxml2-python is needed by yum-utils-1.1.31-54.el7_8.noarch
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下载libxml2-python-2.9.1-6.el7.5.x86_64.rpm安装，报错版本不符，与已有的包冲突

Preparing...                          ################################# [100%]
        package libxml2-2.9.1-6.el7_9.6.x86_64 (which is newer than libxml2-2.9.1-6.el7.5   .x86_64) is already installed
        file /usr/bin/xmlcatalog from install of libxml2-2.9.1-6.el7.5.x86_64 conflicts w   ith file from package libxml2-2.9.1-6.el7_2.3.x86_64
        file /usr/bin/xmllint from install of libxml2-2.9.1-6.el7.5.x86_64 conflicts with    file from package libxml2-2.9.1-6.el7_2.3.x86_64
        file /usr/lib64/libxml2.so.2.9.1 from install of libxml2-2.9.1-6.el7.5.x86_64 con   flicts with file from package libxml2-2.9.1-6.el7_2.3.x86_64
        file /usr/bin/xmlcatalog from install of libxml2-2.9.1-6.el7.5.x86_64 conflicts w   ith file from package libxml2-2.9.1-6.el7_9.6.x86_64
        file /usr/bin/xmllint from install of libxml2-2.9.1-6.el7.5.x86_64 conflicts with    file from package libxml2-2.9.1-6.el7_9.6.x86_64
        file /usr/lib64/libxml2.so.2.9.1 from install of libxml2-2.9.1-6.el7.5.x86_64 con   flicts with file from package libxml2-2.9.1-6.el7_9.6.x86_64
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仍然去update上找，没有找到，最后在CSDN上找到的，花了9.9

rpm -ivh libxml2-python-2.9.1-6.el7_9.6.x86_64.rpm
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尝试使用yum，发现可以了