python升级导致yum使用报错

今天计划安装walle2.0，按官方文档http://www.walle-web.io/docs/index.html一步步进行

进行到这一步突然报错

yum install -y mariadb-devel gcc gcc-c++ python-devel

刚开始怀疑是不是yum源出问题了，把阿里云的源重新下载加载

cp /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.bak
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
wget -P /etc/yum.repos.d/ http://mirrors.aliyun.com/repo/epel-7.repo 
yum clean all  
yum makecache

发现不行，还是报错

检查下python版本

# python
Python 2.7.5 (default, Oct 30 2018, 23:45:53)

发现python已经被升级到2.7.5，而yum需要的python版本是2.6，导致的报错

修改yum启动文件前缀

# cat /usr/bin/yum
#!/usr/bin/python2.7

发现没有用，没有备份，python直接被更新到2.7.5，yum用的库不能加载，不能加载模块

There was a problem importing one of the Python modules
required to run yum. The error leading to this problem was:

   No module named yum

Please install a package which provides this module, or
verify that the module is installed correctly.

查找资料，尝试再安装个python2.6.6版本，修改yum启动文件，但是还是出现模块不能加载

重装python和yum

1、卸载现有的python，强制删除已安装程序及其关联

rpm -qa|grep python|xargs rpm -ev --allmatches --nodeps

强制删除所有残余文件

whereis python |xargs rm -frv

2、卸载现有的yum

rpm -qa|grep yum|xargs rpm -ev --allmatches --nodeps

强制删除所有残余文件

whereis yum |xargs rm -frv

3、下载版本对应的rpm包

wget http://mirrors.ustc.edu.cn/centos/7/os/x86_64/Packages/libxml2-python-2.9.1-6.el7_2.3.x86_64.rpm

wget http://mirrors.ustc.edu.cn/centos/7/os/x86_64/Packages/rpm-4.11.3-35.el7.x86_64.rpm
wget http://mirrors.ustc.edu.cn/centos/7/os/x86_64/Packages/rpm-build-4.11.3-35.el7.x86_64.rpm
wget http://mirrors.ustc.edu.cn/centos/7/os/x86_64/Packages/rpm-build-libs-4.11.3-35.el7.x86_64.rpm
wget http://mirrors.ustc.edu.cn/centos/7/os/x86_64/Packages/rpm-libs-4.11.3-35.el7.x86_64.rpm
wget http://mirrors.ustc.edu.cn/centos/7/os/x86_64/Packages/rpm-sign-4.11.3-35.el7.x86_64.rpm
wget http://mirrors.ustc.edu.cn/centos/7/os/x86_64/Packages/rpm-python-4.11.3-35.el7.x86_64.rpm

wget http://mirrors.ustc.edu.cn/centos/7/os/x86_64/Packages/python-2.7.5-76.el7.x86_64.rpm
wget http://mirrors.ustc.edu.cn/centos/7/os/x86_64/Packages/python-devel-2.7.5-76.el7.x86_64.rpm
wget http://mirrors.ustc.edu.cn/centos/7/os/x86_64/Packages/python-libs-2.7.5-76.el7.x86_64.rpm
wget http://mirrors.ustc.edu.cn/centos/7/os/x86_64/Packages/python-pycurl-7.19.0-19.el7.x86_64.rpm
wget http://mirrors.ustc.edu.cn/centos/7/os/x86_64/Packages/python-setuptools-0.9.8-7.el7.noarch.rpm
wget http://mirrors.ustc.edu.cn/centos/7/os/x86_64/Packages/python-urlgrabber-3.10-9.el7.noarch.rpm
wget http://mirrors.ustc.edu.cn/centos/7/os/x86_64/Packages/python-iniparse-0.4-9.el7.noarch.rpm
wget http://mirrors.ustc.edu.cn/centos/7/os/x86_64/Packages/python-backports-1.0-8.el7.x86_64.rpm
wget http://mirrors.ustc.edu.cn/centos/7/os/x86_64/Packages/python-backports-ssl_match_hostname-3.5.0.1-1.el7.noarch.rpm
wget http://mirrors.ustc.edu.cn/centos/7/os/x86_64/Packages/python-chardet-2.2.1-1.el7_1.noarch.rpm
wget http://mirrors.ustc.edu.cn/centos/7/os/x86_64/Packages/python-ipaddress-1.0.16-2.el7.noarch.rpm
wget http://mirrors.ustc.edu.cn/centos/7/os/x86_64/Packages/python-kitchen-1.1.1-5.el7.noarch.rpm
wget http://mirrors.ustc.edu.cn/centos/7/os/x86_64/Packages/python-virtualenv-15.1.0-2.el7.noarch.rpm

wget http://mirrors.ustc.edu.cn/centos/7/os/x86_64/Packages/yum-3.4.3-161.el7.centos.noarch.rpm
wget http://mirrors.ustc.edu.cn/centos/7/os/x86_64/Packages/yum-metadata-parser-1.1.4-10.el7.x86_64.rpm
wget http://mirrors.ustc.edu.cn/centos/7/os/x86_64/Packages/yum-utils-1.1.31-50.el7.noarch.rpm
wget http://mirrors.ustc.edu.cn/centos/7/os/x86_64/Packages/yum-plugin-fastestmirror-1.1.31-50.el7.noarch.rpm
wget http://mirrors.ustc.edu.cn/centos/7/os/x86_64/Packages/yum-plugin-protectbase-1.1.31-50.el7.noarch.rpm
wget http://mirrors.ustc.edu.cn/centos/7/os/x86_64/Packages/yum-plugin-aliases-1.1.31-50.el7.noarch.rpm

下载完成后安装这些包(--force强制安装)

rpm -Uvh --force --nodeps --replacepkgs *.rpm

安装完这些rpm包后，yum就可以正常使用了，如果还是报下面这个，说明你rpm包没下载全

There was a problem importing one of the Python modules
required to run yum. The error leading to this problem was:

   /usr/lib64/python2.7/site-packages/rpm/_rpm.so: undefined symbol: rpmpkgVerifySi

Please install a package which provides this module, or
verify that the module is installed correctly.

It's possible that the above module doesn't match the
current version of Python, which is:
2.7.5 (default, Apr 11 2018, 07:36:10)
[GCC 4.8.5 20150623 (Red Hat 4.8.5-28)]

If you cannot solve this problem yourself, please go to
the yum faq at:
  http://yum.baseurl.org/wiki/Faq

接着按walle官方文档一步步安装，就很顺利安装完了，大功告成~ ：）

重要的事情说三遍