# apt-cdrom add precise-alternate-amd64.iso
Using CD-ROM mount point /media/apt/
Identifying.. [a85e83d84252d3649a5d86e73a40d8d5-2]
Scanning disc for index files..
Found 0 package indexes, 0 source indexes, 0 translation indexes and 0 signatures
W: Failed to mount '/dev/sr0' to '/media/apt/'
E: Unable to locate any package files, perhaps this is not a Debian Disc or the wrong architecture?