一、先将iso镜像文件挂载
#mount /dev/cdrom /mnt
将cdrom挂载到/mnt下
删除/etc/yum.repos.d/ 目录下所有文件
新建文件local.repo
vi /etc/yum.repos.d/local.repo
[InstallMedia]
name=CentOS Linux 8
baseurl=file:///mnt/BaseOS
gpgcheck=0
enabled=1
[AppStream]
name=AppStream
baseurl=file:///mnt/AppStream
enabled=1
gpgcheck=0
保存文件local.repo
yum源新建缓存，检查文件：
yum makecache
yum repolist
三、还有一种方法，把iso下源文件全部拷贝进系统，新建目录/yum,再对应目录配置yum源文件
cp -rf /mnt/ /yum/
四、DNF的主要命令
$ dnf --help
usage: dnf [options] COMMAND
List of Main Commands:
alias List or create command aliases
autoremove remove all unneeded packages that were originally installed as dependencies
check check for problems in the packagedb
check-update check for available package upgrades
clean remove cached data
deplist List package's dependencies and what packages provide them
distro-sync synchronize installed packages to the latest available versions
downgrade Downgrade a package
group display, or use, the groups information
help display a helpful usage message
history display, or use, the transaction history
info display details about a package or group of packages
install install a package or packages on your system
list list a package or groups of packages
makecache generate the metadata cache
mark mark or unmark installed packages as installed by user.
module Interact with Modules.
provides find what package provides the given value
reinstall reinstall a package
remove remove a package or packages from your system
repolist display the configured software repositories
repoquery search for packages matching keyword
repository-packages run commands on top of all packages in given repository
search search package details for the given string
shell run an interactive DNF shell
swap run an interactive dnf mod for remove and install one spec
updateinfo display advisories about packages
upgrade upgrade a package or packages on your system
upgrade-minimal upgrade, but only 'newest' package match which fixes a problem that affects your system
DNF最后的这个upgrade-minimal命令，貌似Yum没有，这个命令看着很不错。总之，能用DNF，就不要再用yum了。