Well for example
On my Imac, the cdrom drive is located at:
/dev/disk1s1s2
And the hard drive is at:
/dev/disk0s10
To find the CDROM, an easy way to locate your cdrom is in the terminal type:
mount
You'll see output. Find the name of the CDROM you've inserted, for example
/dev/disk1s1s2 on /Volumes/my backup 36 (local, nodev, nosuid, read-only)
is my cdrom driver
and
/dev/disk0s9 on / (local)
is my hard drive.
Easy stuff!
so to make an ISO of that cd, in the terminal I would type
bash-2.05a$ dd if=/dev/disk1s1 of=Backup.iso
dd creates a duplicated disc (now what the initials stand for) copy
http://www.mcsr.olemiss.edu/cgi-bin/man-cgi?dd+1
dd - convert and copy a file
SYNOPSIS
dd [option=value] ...
DESCRIPTION
dd copies the specified input file to the specified output with possible
conversions. The standard input and output are used by default. The
input and output block sizes can be specified to take advantage of raw
physical I/O. dd processes supplementary code-set characters according
to the locale specified in the LC_CTYPE environment variable (see LANG in
environ(5)), except as noted below.
Option Values
if=file Input filename; standard input is default.
of=file Output filename; standard output is default.