地址： https://www.cnblogs.com/magicpose/p/11905330.html

# file: /etc/yum.repos.d/CentOS-AppStream.repo
[AppStream]
name=CentOS-$releasever - AppStream
baseurl=http://mirrors.aliyun.com/centos/$releasever/AppStream/$basearch/os/
gpgcheck=1
enabled=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-centosofficial

# file: /etc/yum.repos.d/CentOS-Base.repo

[BaseOS]
name=CentOS-$releasever - Base
baseurl=http://mirrors.aliyun.com/centos/$releasever/BaseOS/$basearch/os/
gpgcheck=1
enabled=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-centosofficial

# file: /etc/yum.repos.d/CentOS-Epel.repo

[epel]
name=CentOS-$releasever - Epel
baseurl=http://mirrors.aliyun.com/epel/8/Everything/$basearch
enabled=1
gpgcheck=0

以iso光盘镜像作为yum源

需要先挂载光盘，虚拟机安装为例

$ df -h
文件系统             容量  已用  可用 已用% 挂载点
devtmpfs             3.8G     0  3.8G    0% /dev
tmpfs                3.9G     0  3.9G    0% /dev/shm
tmpfs                3.9G   18M  3.8G    1% /run
tmpfs                3.9G     0  3.9G    0% /sys/fs/cgroup
/dev/mapper/cl-root   50G  6.4G   44G   13% /
/dev/mapper/cl-home   42G  427M   41G    2% /home
/dev/sda1            976M  186M  724M   21% /boot
tmpfs                780M   28K  780M    1% /run/user/42
tmpfs                780M  5.7M  774M    1% /run/user/1000
/dev/sr0             6.7G  6.7G     0  100% /run/media/wesson/CentOS-8-BaseOS-x86_64

# sudo mount -o loop /dev/sr0 /media/CentOS

修改配置

# file: /etc/yum.repos.d/CentOS-Media.repo

[c8-media-BaseOS]
name=CentOS-BaseOS-$releasever - Media
baseurl=file:///media/CentOS/BaseOS/
gpgcheck=1
enabled=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-centosofficial
[c8-media-AppStream]
name=CentOS-AppStream-$releasever - Media
baseurl=file:///media/CentOS/AppStream/
gpgcheck=1
enabled=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-centosofficial

重载

dnf clean all   # 清除所有的缓存文件
dnf makecache   # 制作元数据缓存