由于Redhat的yum在线更新是收费的，如果没有注册的话是不能使用的，即不能在线安装软件。所以yum install 命令每次都安装失败
下面介绍一种更改yum源的方式：
系统说明：
系统：Red Hat Enterprise Linux Server 6.3
内核：Linux 2.6.32-279.el6.x86_64
1、删除RHEL原有的yum
rpm -aq|grep yum|xargs rpm -e --nodeps
2、下载新的yum安装包 #这里我们使用CentOS的yum源
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-3.2.29-60.el6.centos.noarch.rpm wget http://mirrors.163.com/centos/6/os/x86_64/Packages/yum-plugin-fastestmirror-1.1.30-30.el6.noarch.rpm
提示：
a、如果下载时提示404找不到错误，请访问http://mirrors.163.com/centos/6/os/x86_64 /Packages/，手动查找上面四个包，有时候版本会有点小偏差
b、如果提示正在解析主机 mirrors.163.com... 失败：未知的名称或服务。 wget: 无法解析主机地址 “mirrors.163.com"，点击这里
3、安装yum软件包
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-3.2.29-60.el6.centos.noarch.rpm yum-plugin-fastestmirror-1.1.30-30.el6.noarch.rpm
(由于最后两个安装包是相互依赖的，所以要一起安装，如果出现“xxx is needed by xxx”，根据提示下载需要的安装包，如果出现类似file /usr/lib/python2.6/site-packages/urlgrabber/grabber.py from install of python-urlgrabber-3.9.1-11.el6.noarch conflicts with file from package python-urlgrabber-3.9.1-8.el6.noarch提示，点击这里)
4、更改yum源 #我们使用网易的CentOS镜像源
cd /etc/yum.repos.d/ wget http://mirrors.163.com/.help/CentOS6-Base-163.repo vi CentOS6-Base-163.repo
编辑文件，把文件里面的$releasever全部替换为版本号，即6 最后保存， 或者直接把下面的内存拷贝到CentOS6-Base-163.repo文件中即可
（已经修改好，不用下载直接新建CentOS6-Base-163.repo 也可以）
# CentOS-Base.repo # # The mirror system uses the connecting IP address of the client and the # update status of each mirror to pick mirrors that are updated to and # geographically close to the client. You should use this for CentOS updates # unless you are manually picking other mirrors. # # If the mirrorlist= does not work for you, as a fall back you can try the # remarked out baseurl= line instead. # # [base] name=CentOS-6 - Base - 163.com baseurl=http://mirrors.163.com/centos/6/os/$basearch/ #mirrorlist=http://mirrorlist.centos.org/?release=6&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=6&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=6&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=6&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=6&arch=$basearch&repo=contrib gpgcheck=1 enabled=0 gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6
5、收尾，测试YUM 是否可用
yum clean all
#清理yum缓存
yum makecache
#将服务器上的软件包信息缓存到本地,以提高搜索安装软件的速度
yum install gcc*
#测试yum是否可用
