本例使用一台服务器，配置yum源服务器，其它机器可以通过该服务器建立yum源。
三台机器：
yum源服务器：
172.16.22.110
另外两台客户机：
172.16.22.180 centos74.
172.16.23.198 centos7.3
1、上传对应iso镜像，本例中只列举两个，一个centos7.4的镜像，一个centos7.3的镜像；
root@scc[/root]#ll
-rw-r--r--. 1 root root 8694792192 Aug 13 18:59 CentOS-7.4-x86_64-Everything-1708.iso
-rw-r--r--. 1 root root 8280604672 Aug 21 2017 CentOS-7-x86_64-Everything-1611.iso
2、镜像服务器安装http服务
mount -o loop /root/CentOS-7-x86_64-Everything-1611.iso /mnt
vi /etc/yum.repos.d/local.repo
[centos7.3]
name=centos7.3
baseurl=file:///mnt
enabled=1
gpgcheck=0
保存退出。
yum update
配置了本地yum源。
然后安装http服务
yum -y install httpd
启动并添加自启动
systemctl start httpd
systemctl enable httpd
3、在/var/www/html/目录下建立对应挂载点
cd /var/www/html
mkdir centos7.3
mkdir centos7.4
4、修改/etc/fstab文件
添加如下内容：
/root/CentOS-7-x86_64-Everything-1611.iso /var/www/html/centos7.3 iso9660 defaults,ro,loop 0 0
/root/CentOS-7.4-x86_64-Everything-1708.iso /var/www/html/centos7.4 iso9660 defaults,ro,loop 0 0
保存退出，然后
mount -a
df -Th
/dev/loop0 iso9660 8.1G 8.1G 0 100% /var/www/html/centos7.4
/dev/loop1 iso9660 7.8G 7.8G 0 100% /var/www/html/centos7.3
确认挂载成功。
5、配置客户机
先看centos7.3
root@myhost1[/etc/yum.repos.d]#cat /etc/redhat-release
CentOS Linux release 7.3.1611 (Core)
配置文件
root@myhost1[/etc/yum.repos.d]#vi file.repo
[http]
name=http_centos7.3
baseurl=http://172.16.22.110/centos7.3
gpgcheck=0
enabled=1
保存退出。
root@myhost1[/etc/yum.repos.d]#yum clean all
Loaded plugins: fastestmirror
Cleaning repos: http
Cleaning up everything
Cleaning up list of fastest mirrors
root@myhost1[/etc/yum.repos.d]#yum makecache
Loaded plugins: fastestmirror
http | 3.6 kB 00:00:00
(1/4): http/group_gz | 155 kB 00:00:00
(2/4): http/filelists_db | 6.6 MB 00:00:00
(3/4): http/primary_db | 5.6 MB 00:00:00
(4/4): http/other_db | 2.4 MB 00:00:00
Determining fastest mirrors
Metadata Cache Created
root@myhost1[/etc/yum.repos.d]#
6、在看centos7.4
root@myhost1[/etc/yum.repos.d]#cat /etc/redhat-release
CentOS Linux release 7.4.1708 (Core)
root@myhost1[/etc/yum.repos.d]#cat file.repo
[http]
name=centos7-Server
baseurl=http://172.16.22.110/centos7.4
enabled=1
gpgcheck=0
root@myhost1[/etc/yum.repos.d]#yum clean all
Loaded plugins: fastestmirror
Cleaning repos: http
Cleaning up everything
Maybe you want: rm -rf /var/cache/yum, to also free up space taken by orphaned data from disabled or removed repos
root@myhost1[/etc/yum.repos.d]#yum makecache
Loaded plugins: fastestmirror
http | 3.6 kB 00:00:00
(1/4): http/group_gz | 156 kB 00:00:00
(2/4): http/primary_db | 5.7 MB 00:00:00
(3/4): http/filelists_db | 6.7 MB 00:00:00
(4/4): http/other_db | 2.5 MB 00:00:00
Determining fastest mirrors
Metadata Cache Created
root@myhost1[/etc/yum.repos.d]#
都没问题。