最近由于要进行性能测试，在虚拟机中安装：yum -y install httpd-tools  ;出现如下错误：

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

   /lib64/libnssutil3.so: undefined symbol: PR_GetEnvSecure

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, Aug  4 2017, 00:39:18) 
[GCC 4.8.5 20150623 (Red Hat 4.8.5-16)]

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

、

查看python版本

# python -V

Python 2.7.3

#whereis python

python: /usr/bin/python /usr/bin/python2.7 /usr/lib/python2.7 /usr/lib64/python2.4 /usr/lib64/python2.7 /etc/python /usr/local/bin/python2.4 /usr/include/python2.7 /usr/share/man/man1/python.1.gz

最近从python 2.4升级到python2.7 导致 yum 不可用，

原因主要是yum 不支持python27 因此需要更改yum的可用路径

which yum

查看下yum的安装路径

/usr/bin/yum

vi /usr/bin/yum

更改#!/usr/bin/python 为#!/usr/bin/python2.6

再次运行就正常了