If you have copied the Red Hat 7 ISO image to a directory on the system, you can mount the ISO image file by running the following command:
# mount -o loop /var/rhel7iso/rhel-server-7.0-x86_64-dvd.iso /mnt
Note: The loop option tells the mount command that what is being mounted is not a block mountable device file but a mountable image file.
# df -h | grep mnt
To mount from DVD:
# mount /dev/cdrom /mnt