[CenOS8-Base]
name=CenOS8-Base
baseurl=file:///mnt/cdrom/BaseOS
gpgcheck=0
enabled=1

[CenOS8-AppStream]
name=CenOS8-AppStream
baseurl=file:///mnt/cdrom/AppStream
gpgcheck=0
enabled=1

配置

[root@localhost ~]# lsblk 
NAME        MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sr0          11:0    1 10.1G  0 rom  /run/media/root/CentOS-8-5-2111-x86_64-dvd
nvme0n1     259:0    0   20G  0 disk 
├─nvme0n1p1 259:1    0  300M  0 part /boot
├─nvme0n1p2 259:2    0    2G  0 part [SWAP]
└─nvme0n1p3 259:3    0 17.7G  0 part /
[root@localhost ~]# mkdir /mnt/cdrom
[root@localhost ~]# mount /dev/cdrom /mnt/cdrom/
mount: /mnt/cdrom: WARNING: device write-protected, mounted read-only.
[root@localhost ~]# rm -rf /etc/yum.repos.d/*
[root@localhost ~]# vim /etc/yum.repos.d/local.repo
[root@localhost ~]# cat /etc/yum.repos.d/local.repo
[CenOS8-Base]
name=CenOS8-Base
baseurl=file:///mnt/cdrom/BaseOS
gpgcheck=0
enabled=1

[CenOS8-AppStream]
name=CenOS8-AppStream
baseurl=file:///mnt/cdrom/AppStream
gpgcheck=0
enabled=1
[root@localhost ~]# yum makecache 
CenOS8-Base                                                                                  139 MB/s | 2.6 MB     00:00
CenOS8-AppStream                                                                             107 MB/s | 7.5 MB     00:00
Metadata cache created.
[root@localhost ~]#