因Redhat 的（yum）更新包只对注册的用户生效，所以我们使用centos7.0的yum才能正常使用
以下操作本人已实机操作成功。
注意:系统版本一定要相同。
系统：RedHat Enterprise Linux 7.0-x86_64
[root@RHEL7-anker ~]# cat /etc/redhat-release
Red Hat Enterprise Linux Server release 7.0 (Maipo)
操作步骤如下：
1.首先查看redhat 7.0系统本身所安装的哪些yum 软件包：
rpm -qa | grep yum #列出所有已安装的yum包
2.删除这些包：
命令：rpm -qa | grep yum |xargs rpm -e --nodeps #删除所有以前的yum包
命令执行结束后再次执行：rpm -qa | grep yum
没有结果即为删除成功
3.下载相关安装包RPM
wget http://mirrors.163.com/centos/7/os/x86_64/Packages/python-iniparse-0.4-9.el7.noarch.rpm
wget http://mirrors.163.com/centos/7/os/x86_64/Packages/yum-3.4.3-150.el7.centos.noarch.rpm
wget http://mirrors.163.com/centos/7/os/x86_64/Packages/yum-metadata-parser-1.1.4-10.el7.x86_64.rpm
wget http://mirrors.163.com/centos/7/os/x86_64/Packages/yum-plugin-fastestmirror-1.1.31-40.el7.noarch.rpm
4.安装下载的安装包（如果下载不到或者安装依赖太多可以直接使用文章最后提供的包需要积分哦）
[root@RHEL7-anker Downloads]#rpm -ivh python-iniparse-0.4-9.el7.noarch.rpm
[root@RHEL7-anker Downloads]#rpm -ivh yum-metadata-parser-1.1.4-10.el7.x86_64.rpm
[root@RHEL7-anker Downloads]#rpm -ivh yum-3.4.3-150.el7.centos.noarch.rpm yum-plugin-fastestmirror-1.1.31-40.el7.noarch.rpm --nodeps
注：最后两个rpm要一起安装，不能单个安装,注意后面加上--nodeps参数，不加的话会有依赖问题
5.centos7.0的系统
[root@CentOS7 ~]# cat /etc/redhat-release
CentOS Linux release 7.3.1611 (Core)
将centos7.0的系统中的yum源文件 /etc/yum.repos.d/CentOS-Base.repo复制到当前操作系统RedHat Enterprise Linux 7.0-x86_64 的 /etc/yum.repos.d/目录下
6.将centos7.0的系统中的/etc/pki/rpm-gpg/*文件复制到当前操作系统RedHat Enterprise Linux 7.0-x86_64 的/etc/pki/rpm-gpg/目录下
7.将复制过来的Centos-Base.repo中的$releasever改为Centos的版本号即可
执行命令：sed -i 's#$releasever#7#g' CentOS-Base.repo
cat CentOS-Base.repo
结果如下
# 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
#mirrorlist=http://mirrorlist.centos.org/?release=7&arch=$basearch&repo=os
baseurl=http://mirror.centos.org/centos/7/os/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
#released updates
[updates]
name=CentOS-7 - Updates
#mirrorlist=http://mirrorlist.centos.org/?release=7&arch=$basearch&repo=updates
baseurl=http://mirror.centos.org/centos/7/updates/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
#additional packages that may be useful
[extras]
name=CentOS-7 - Extras
#mirrorlist=http://mirrorlist.centos.org/?release=7&arch=$basearch&repo=extras
baseurl=http://mirror.centos.org/centos/7/extras/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-7 - Plus
#mirrorlist=http://mirrorlist.centos.org/?release=7&arch=$basearch&repo=centosplus
baseurl=http://mirror.centos.org/centos/7/centosplus/$basearch/
gpgcheck=1
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
注意，红色的是修改后的，原为$releasever,改成的7为版本号.
8.将修改后的Centos-Base.repo文件复制到/etc/yum.repos.d/目录下.
9. yum clean all 清除原有缓存
[root@RHEL7-anker yum.repos.d]# yum clean all
Loaded plugins: fastestmirror, product-id, subscription-manager
This system is not registered to Red Hat Subscription Management. You can use subscription-manager to register.
Cleaning repos: base extras updates
Cleaning up everything
Cleaning up list of fastest mirrors
10. yum makecache 获取yum列表
[root@RHEL7-anker yum.repos.d]# yum makecache
Loaded plugins: fastestmirror, product-id, subscription-manager
This system is not registered to Red Hat Subscription Management. You can use subscription-manager to register.
base | 3.6 kB 00:00:00
extras | 3.4 kB 00:00:00
updates | 3.4 kB 00:00:00
(1/12): base/x86_64/group_gz | 155 kB 00:00:00
(2/12): base/x86_64/filelists_db | 6.6 MB 00:00:38
base/x86_64/primary_db FAILED ] 155 kB/s | 11 MB 00:12:21 ETA
http://mirror.centos.org/centos/7/os/x86_64/repodata/bd50ff3d861cc21d254a390a963e9f0fd7b7b96ed9d31ece2f2b1997aa3a056f-primary.sqlite.bz2: [Errno 12] Timeout on http://120.192.95.138:801/cache/mirror.centos.org/centos/7/os/x86_64/repodata/bd50ff3d861cc21d254a390a963e9f0fd7b7b96ed9d31ece2f2b1997aa3a056f-primary.sqlite.bz2?ich_args=e27b6e155c53ff9bc20853c8be611065_1_0_0_5_94fb044d9b84bf033d68857cb366e888353663b5330c20986259f828775ea78f_85f301fcd124012562514a55b9ed13c1_1_0&ich_ip=159-135: (28, 'Operation too slow. Less than 1000 bytes/sec transferred the last 30 seconds')
Trying other mirror.
(3/12): extras/x86_64/prestodelta | 149 kB 00:00:04
(4/12): extras/x86_64/primary_db | 191 kB 00:00:01
(5/12): updates/x86_64/prestodelta | 954 kB 00:00:02
(6/12): extras/x86_64/filelists_db | 1.1 MB 00:00:09
(7/12): extras/x86_64/other_db | 905 kB 00:00:07
(8/12): base/x86_64/other_db | 2.4 MB 00:00:16
(9/12): updates/x86_64/filelists_db | 4.4 MB 00:00:21
(10/12): base/x86_64/primary_db | 5.6 MB 00:00:12
(11/12): updates/x86_64/primary_db | 7.8 MB 00:00:51
updates/x86_64/other_db FAILED ========- ] 81 B/s | 54 MB 247:20:22 ETA
http://mirror.centos.org/centos/7/updates/x86_64/repodata/36288cdc93433b594aed022edabca28fe92c3497e23da598c59f890c0ddd7255-other.sqlite.bz2: [Errno 12] Timeout on http://mirror.centos.org/centos/7/updates/x86_64/repodata/36288cdc93433b594aed022edabca28fe92c3497e23da598c59f890c0ddd7255-other.sqlite.bz2: (28, 'Operation too slow. Less than 1000 bytes/sec transferred the last 30 seconds')
Trying other mirror.
updates/x86_64/other_db FAILED ===================- ] 100 B/s | 80 MB 123:36:37 ETA
http://mirror.centos.org/centos/7/updates/x86_64/repodata/36288cdc93433b594aed022edabca28fe92c3497e23da598c59f890c0ddd7255-other.sqlite.bz2: [Errno 12] Timeout on http://mirror.centos.org/centos/7/updates/x86_64/repodata/36288cdc93433b594aed022edabca28fe92c3497e23da598c59f890c0ddd7255-other.sqlite.bz2: (28, 'Operation too slow. Less than 1000 bytes/sec transferred the last 30 seconds')
Trying other mirror.
(12/12): updates/x86_64/other_db | 93 MB 00:03:40
Determining fastest mirrors
Metadata Cache Created
到此yum就可以在线安装软件了。
测试一下是否能安装：
[root@RHEL7-anker ~]# yum install nmap -y
Loaded plugins: fastestmirror, product-id, subscription-manager
This system is not registered to Red Hat Subscription Management. You can use subscription-manager to register.
Loading mirror speeds from cached hostfile
Resolving Dependencies
--> Running transaction check
---> Package nmap.x86_64 2:6.40-7.el7 will be installed
--> Processing Dependency: nmap-ncat = 2:6.40-7.el7 for package: 2:nmap-6.40-7.el7.x86_64
--> Running transaction check
---> Package nmap-ncat.x86_64 2:6.40-4.el7 will be updated
---> Package nmap-ncat.x86_64 2:6.40-7.el7 will be an update
--> Finished Dependency Resolution
Dependencies Resolved
================================================================================
Package Arch Version Repository Size
================================================================================
Installing:
nmap x86_64 2:6.40-7.el7 base 4.0 M
Updating for dependencies:
nmap-ncat x86_64 2:6.40-7.el7 base 201 k
Transaction Summary
================================================================================
Install 1 Package
Upgrade ( 1 Dependent package)
Total download size: 4.2 M
Downloading packages:
No Presto metadata available for base
(1/2): nmap-ncat-6.40-7.el7.x86_64.rpm | 201 kB 00:02
(2/2): nmap-6.40-7.el7.x86_64.rpm | 4.0 MB 00:23
--------------------------------------------------------------------------------
Total 177 kB/s | 4.2 MB 00:24
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
Updating : 2:nmap-ncat-6.40-7.el7.x86_64 1/3
Installing : 2:nmap-6.40-7.el7.x86_64 2/3
Cleanup : 2:nmap-ncat-6.40-4.el7.x86_64 3/3
Verifying : 2:nmap-ncat-6.40-7.el7.x86_64 1/3
Verifying : 2:nmap-6.40-7.el7.x86_64 2/3
Verifying : 2:nmap-ncat-6.40-4.el7.x86_64 3/3
Installed:
nmap.x86_64 2:6.40-7.el7
Dependency Updated:
nmap-ncat.x86_64 2:6.40-7.el7
Complete!
看到Complete!，恭喜你修改成功。
https://download.csdn.net/download/dongshibo12/10335659
或者在CSDN资源搜索：RedHat7_install_CentOS7_yum