christophe at vandeplas.com

From slashdotdash.net

1. Insert CD/DVD source

2. Fire up a Terminal, you can then determine the device that is you CD/DVD drive using the following command:

$ drutil status
 Vendor   Product           Rev 
 MATSHITA DVD-R   UJ-857    HBEA

           Type: CD-ROM               Name: /dev/disk1
      Cur Write:   24x CD           Sessions: 1
      Max Write:   24x CD             Tracks: 1
   Overwritable:   00:00:00         blocks:        0 /   0.00MB /   0.00MiB
     Space Free:   00:00:00         blocks:        0 /   0.00MB /   0.00MiB
     Space Used:   76:47:23         blocks:   345548 / 707.68MB / 674.90MiB
    Writability: 

3. Umount the disk with the following command:

$ diskutil unmountDisk /dev/disk1
Disk /dev/disk1 unmounted

4. Create the ISO file with the dd utility (may take some time):

$ dd if=/dev/disk1s0 of=file.iso bs=2048

5. Test the ISO image by mounting the new file (or open with Finder):

$ hdid file.iso

6. The ISO image can then be burnt to a blank CD/DVD.