mkdir /mnt/cdrom/

cd /etc/yum.repos.d/
mv CentOS-Base.repo   CentOS-Base.repo.bak
vi cdrom.repo
[name]
name=yum
gpgcheck=0
enabled=1
baseurl=file:///mnt/cdrom/

ls /etc/yum.repos.d/
cdrom.repo  CentOS-Base.repo.bak  CentOS-Media.repo

mount /dev/cdrom /mnt/cdrom/
挂载光盘到 /mnt/cdrom/下

yum clean all
yum makecache

yum -y install lrzsz

vi cdrom.repo
[name]
name=yum
gpgcheck=0
enabled=1
baseurl=file:///mnt/cdrom/Server