您好，很高兴为您解答。
1.检查是否安装yum包
查看RHEL是否安装了yum，若是安装了，那么又有哪些yum包：
[root@localhost ~]# rpm -qa |grep yum
yum-metadata-parser-1.0-8.fc6
yum-3.0.1-5.el5
yum-rhn-plugin-0.4.3-1.el5
yum-updatesd-3.0.1-5.el5
2 删除redhat自带的yum包
卸载上面显示的所有yum包：
[root@localhost ~]# rpm -qa|grep yum|xargs rpm -e --nodeps（不检查依赖，直接删除rpm包）
再用
[root@localhost ~]# rpm -qa |grep yum
[root@localhost ~]#
查看，无信息显示表示已经卸载完成。
3.下载新的yum包。使用Centos6.5的yum包
# wget http://mirrors.163.com/centos/6.5/os/i386/Packages/yum-metadata-parser-1.1.2-16.el6.i686.rpm# wget http://mirrors.163.com/centos/6.5/os/i386/Packages/yum-3.2.29-40.el6.centos.noarch.rpm
# wget http://mirrors.163.com/centos/6.5/os/i386/Packages/yum-plugin-fastestmirror-1.1.30-14.el6.noarch.rpm
安装yum软件包
注意:单个的安装包可能会依赖其它包（例如yum和yum-fastestmirror会相互依赖），所以我们可以把所有这些包放在一起，用一行命令将它们同时安装即可：
# rpm -ivh yum-metadata-parser-1.1.2-16.el6.i686.rpm yum-3.2.29-40.el6.centos.noarch.rpm yum-plugin-fastestmirror-1.1.30-14.el6.noarch.rpm4.更换yum源。使用163的源
# 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$releasever全部替换为版本号，即6.5 最后保存！或者直接把下面的内存拷贝到CentOS6-Base-163.repo文件中即可（已经修改好）
# CentOS-Base.repo#
# The mirror system uses the connecting IP address of the client and the
# update status of each mirror to pick mirrors that are updated to and
# geographically close to the client. You should use this for CentOS updates
# unless you are manually picking other mirrors.
#
# If the mirrorlist= does not work for you, as a fall back you can try the
# remarked out baseurl= line instead.
#
#
[base]
name=CentOS-6.5 - Base - 163.com
baseurl=http://mirrors.163.com/centos/6.5/os/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=6.5&arch=$basearch&repo=os
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6
#released updates
[updates]
name=CentOS-6.5 - Updates - 163.com
baseurl=http://mirrors.163.com/centos/6.5/updates/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=6.5&arch=$basearch&repo=updates
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6
#additional packages that may be useful
[extras]
name=CentOS-6.5 - Extras - 163.com
baseurl=http://mirrors.163.com/centos/6.5/extras/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=6.5&arch=$basearch&repo=extras
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6
#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-6.5 - Plus - 163.com
baseurl=http://mirrors.163.com/centos/6.5/centosplus/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=6.5&arch=$basearch&repo=centosplus
gpgcheck=1
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6
#contrib - packages by Centos Users
[contrib]
name=CentOS-6.5 - Contrib - 163.com
baseurl=http://mirrors.163.com/centos/6.5/contrib/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=6.5&arch=$basearch&repo=contrib
gpgcheck=1
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6
5.清除原有缓存
# yum clean all重建缓存，以提高搜索安装软件的速度
6.更新系统
# yum update
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~ O(∩_∩)O~
