yum失败
问题：
在CentOS 5.5中需要使用yum安装程序，出现错误:
There was a problem importing one of the Python modulesrequired to run yum. The error leading to this problem was:
/usr/lib/python2.4/site-packages/_sqlitecache.so: wrong ELF class: ELFCLASS32
Please install a package which provides this module, or
verify that the module is installed correctly.
解决办法：
放狗搜，原因是python版本不兼容，办法是卸载原来的yum重新安装；
1. 确定当前CentOS的版本
[root@centos-74 yum.repos.d]# lsb_release -a
LSB Version: :core-3.1-amd64:core-3.1-ia32:core-3.1-noarch:graphics-3.1-amd64:graphics-3.1-ia32:graphics-3.1-noarch
Distributor ID: CentOS
Description: CentOS release 5.5 (Final)
Release: 5.5
Codename: Final
可以看到当前的CentOS版本是5.5；
[root@centos-74 yum.repos.d]# uname -a
Linux centos-74 2.6.18-194.el5 #1 SMP Fri Apr 2 14:58:14 EDT 2010 x86_64 x86_64 x86_64 GNU/Linux
可以看到所安装的是X86_64的系统；
2. 安装yum程序
2.1 从网易的mirrors下载所需要的rpm包；
wget http://mirrors.163.com/centos/5/os/x86_64/CentOS/python-iniparse-0.2.3-4.el5.noarch.rpm
该文件从网易的站点已经下载不到了，只有python-iniparse-0.2.3-6.el5.noarch.rpm，但是python-iniparse-0.2.3-6.el5.noarch.rpm会与其他三个文件存在兼容性问题，所以，放狗搜一下，从其他地方下载python-iniparse-0.2.3-4.el5.noarch.rpm
wget http://mirrors.163.com/centos/5/os/x86_64/CentOS/yum-3.2.22-40.el5.centos.noarch.rpm
wget http://mirrors.163.com/centos/5/os/x86_64/CentOS/yum-fastestmirror-1.1.16-21.el5.centos.noarch.rpm
wget http://mirrors.163.com/centos/5/os/x86_64/CentOS/yum-metadata-parser-1.1.2-4.el5.centos.x86_64.rpm
2.2 安装已经下载的软件包
rpm -ivh --nodeps python-iniparse-0.2.3-4.el5.noarch.rpm yum-3.2.22-40.el5.centos.noarch.rpm yum-metadata-parser-1.1.2-4.el5.centos.x86_64.rpm yum-fastestmirror-1.1.16-21.el5.centos.noarch.rpm
不知为什么，上述命令执行完毕后只提示安装了第一个软件包python-iniparse-0.2.3-4.el5.noarch.rpm
Preparing... ########################################### [100%]
package python-iniparse-0.2.3-4.el5.noarch is already installed
再次安装剩余的软件包，
rpm -ivh --nodeps yum-3.2.22-40.el5.centos.noarch.rpm yum-metadata-parser-1.1.2-4.el5.centos.x86_64.rpm yum-fastestmirror-1.1.16-21.el5.centos.noarch.rpm
Preparing... ########################################### [100%]
1:yum-metadata-parser ########################################### [ 33%]
2:yum-fastestmirror ########################################### [ 67%]
3:yum ########################################### [100%]
通过命令rpm -qa | grep yum查看安装结果
[root@centos-74 zhao]# rpm -qa|grep yum
yum-3.2.22-40.el5.centos
yum-fastestmirror-1.1.16-21.el5.centos
yum-metadata-parser-1.1.2-4.el5
[root@centos-74 zhao]#
导入证书
rpm -import http://mirrors.163.com/centos/RPM-GPG-KEY-CentOS-5
让yum使用网易的源：
#cd /etc/yum.repos.d/
#wget http://mirrors.163.com/.help/CentOS-Base-163.repo
编辑CentOS-Base-163.repo，在所有mirrorlist前面加上#，把所有$releasever替换成5，然后保存。
#yum clean metadata
完成后yum可以正常工作，更新yum
#yum -y upgrade