更换国内Yum源

由于 redhat的yum在线更新是收费的，如果没有注册的话不能使用，如果要使用，需将redhat的yum卸载后，重启安装，再配置其他源
解决办法：
1、首先到http://mirrors.163.com/centos下载软件包

x86 地址：http://mirrors.163.com/centos/6/os/i386/Packages/

x86_64 地址：http://mirrors.163.com/centos/6/os/x86_64/Packages/

必要下载的软件包有（以64位系统为例）：

Python-iniparse-0.3.1-2.1.el6.noarch.rpm

yum-3.2.29-40.el6.centos.noarch.rpm

yum-metadata-parser-1.1.2-16.el6.x86_64.rpm

yum-plugin-fastestmirror-1.1.30-14.el6.noarch.rpm

下载命令：

wget http://mirrors.163.com/centos/6/os/x86_64/Packages/python-iniparse-0.3.1-2.1.el6.noarch.rpm 
wget http://mirrors.163.com/centos/6/os/x86_64/Packages/yum-metadata-parser-1.1.2-16.el6.x86_64.rpm
wget http://mirrors.163.com/centos/6/os/x86_64/Packages/yum-3.2.29-40.el6.centos.noarch.rpm 
wget http://mirrors.163.com/centos/6/os/x86_64/Packages/yum-plugin-fastestmirror-1.1.30-14.el6.noarch.rpm

由于版本不断更新，所以当中有几个rpm包需要自己进入http://mirrors.163.com/centos/6/os/x86_64/Packages/里找命名类似的。

2、卸载RedHat自带的yum

rpm -qa | grep yum | xargs rpm -e --nodeps

xargs作用是将参数列表转换成小块分段传递给其他命令，以避免参数列表过长的问题

--nodeps  强制卸载,不管依赖性

3、安装下载的centos的yum包：

rpm -ivh python-iniparse-0.3.1-2.1.el6.noarch.rpm
rpm -ivh yum-metadata-parser-1.1.2-16.el6.x86_64.rpm 
rpm -ivh yum-3.2.29-81.el6.centos.noarch.rpm yum-plugin-fastestmirror-1.1.30-40.el6.noarch.rpm

[注] :最后2个需要一起安装，否则会出现依赖性错误

	rpm -ivh yum-3.2.29-81.el6.centos.noarch.rpm 
	warning: yum-3.2.29-81.el6.centos.noarch.rpm: Header V3 RSA/SHA1 Signature, key ID c105b9de: NOKEY
	error: Failed dependencies:
        	yum-plugin-fastestmirror is needed by yum-3.2.29-81.el6.centos.noarch

4、到http://mirrors.163.com的 Centos帮助文档 中下载CentOS6-Base-163.repo文件，存放到/etc/yum.repos.d中

wget http://mirrors.163.com/.help/CentOS6-Base-163.repo

编辑CentOS6-Base-163.repo文件，将其中所有的$releasever更改为centos的版本号

[root@KWM yum.repos.d]# cat CentOS6-Base-163.repo 
# CentOS-Base.repo
#
# The mirror system uses the connecting IP address of the client and the
# update status of each mirror to pick mirrors that are updated to and
# geographically close to the client.  You should use this for CentOS updates
# unless you are manually picking other mirrors.
#
# If the mirrorlist= does not work for you, as a fall back you can try the 
# remarked out baseurl= line instead.
#
#

[base]
name=CentOS-6 - Base - 163.com
baseurl=http://mirrors.163.com/centos/6/os/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6

#released updates 
[updates]
name=CentOS-6 - Updates - 163.com
baseurl=http://mirrors.163.com/centos/6/updates/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=updates
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6

#additional packages that may be useful
[extras]
name=CentOS-6 - Extras - 163.com
baseurl=http://mirrors.163.com/centos/6/extras/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=extras
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6

#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-6 - Plus - 163.com
baseurl=http://mirrors.163.com/centos/6/centosplus/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=centosplus
gpgcheck=1
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6

#contrib - packages by Centos Users
[contrib]
name=CentOS-6 - Contrib - 163.com
baseurl=http://mirrors.163.com/centos/6/contrib/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=contrib
gpgcheck=1
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6

6、yum clean all 清除原有缓存
7、yum makecache  获取yum列表
出现下面提示，表示yum更改完成：
Metadata Cache Created  元数据缓存已建立