一、故障现象：
在安装了Read linux后，使用yum安装软件，出现如下提示：
[root@localhost~]# yum install xxx
Loaded plugins: product-id, search-disabled-repos, subscription-manager
This system is not registered with an entitlement server. You can use subscription-manager to register.
There are no enabled repos.
Run "yum repolist all" to see the repos you have.
To enable Red Hat Subscription Management repositories:
subscription-manager repos --enable <repo>
To enable custom repositories:
yum-config-manager --enable <repo>
二、解决办法：
1、查看redhat 7.0系统本身所安装的那些yum软件包
[root@localhost~]# rpm -qa | grep yum
yum-rhn-plugin-2.0.1-10.el7.noarch
yum-metadata-parser-1.1.4-10.el7.x86_64
yum-3.4.3-158.el7.noarch
2、卸载这些软件包
[root@localhost~]# rpm -qa | grep yum | xargs rpm -e --nodeps
[root@localhost~]# rpm -e yum-rhn-plugin-2.0.1-10.el7.noarch --nodeps
[root@localhost~]# rpm -e yum-metadata-parser-1.1.4-10.el7.x86_64 --nodeps
[root@localhost~]# rpm -e yum-3.4.3-158.el7.noarch --nodeps
3、下载RPM包并上传到readlinux(请根据版本自行更换URL)
http://mirrors.163.com/centos/7/os/x86_64/Packages/
python-kitchen*，python-chardet*，yum-utils*，yum-metadata-parser*，yum-3.4.3-163.el7.centos.noarch.rpm yum-utils*，yum-updateonboot*，yum-plugin-fastestmirror*
4、安装软件包
rpm -ivh python-*
rpm -ivh yum-*
5、新建repo 配置文件（如果是其他版本，则将下面的7改为你当前的版本数字）
vim /etc/yum.repos.d/CentOS-Base.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-$7 - Base - 163.com
#mirrorlist=http://mirrorlist.centos.org/?release=$7&arch=$basearch&repo=os
baseurl=http://mirrors.163.com/centos/7/os/$basearch/
gpgcheck=1
gpgkey=http://mirrors.163.com/centos/RPM-GPG-KEY-CentOS-7
#released updates
[updates]
name=CentOS-$7 - Updates - 163.com
#mirrorlist=http://mirrorlist.centos.org/?release=$7&arch=$basearch&repo=updates
baseurl=http://mirrors.163.com/centos/7/updates/$basearch/
gpgcheck=1
gpgkey=http://mirrors.163.com/centos/RPM-GPG-KEY-CentOS-7
#additional packages that may be useful
[extras]
name=CentOS-$7 - Extras - 163.com
#mirrorlist=http://mirrorlist.centos.org/?release=$7&arch=$basearch&repo=extras
baseurl=http://mirrors.163.com/centos/7/extras/$basearch/
gpgcheck=1
gpgkey=http://mirrors.163.com/centos/RPM-GPG-KEY-CentOS-7
#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-$7 - Plus - 163.com
baseurl=http://mirrors.163.com/centos/7/centosplus/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirrors.163.com/centos/RPM-GPG-KEY-CentOS-7
6、测试一下就对了
yum clean all && yum makecache
**********如果难得执行上面的1-5步骤，直接的把每6步写好的RPO文件，放到/etc/yum.repos.d也能用**********