Insert your CD/DVD. Check that MacOS has mounted it in as a Volume (It will appear on the Desktop).
Identify which device the CD/DVD is.
This is the trickiest part of the whole procedure. First, use
drutilto get some comprehensive information about your CD/DVD
$ drutil status Vendor Product Rev HL-DT-ST DVDRW GS21N SA15 Type: CD-ROM Name: /dev/disk4 Sessions: 1 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: 30:12:40 blocks: 135940 / 278.41MB / 265.51MiB Writability:
Note the device name here (
/dev/disk4) and the “Space Used” (265.51MiB). If you do everything right, your iso file should end up with the size that you see here.
/dev/disk4may not be the right device yet, however. It may be that you have to use a subdevice. Check which device MacOS used for mounting the CD. In my example, I got this:
$ df -h /dev/disk4s1s2 50Mi 50Mi 0Bi 100% /Volumes/hp LaserJet 1010 Series
This CD is pretty special. It contains printer drivers for both Windows and Mac, and is split in two parts. Mac OS only mounted the Mac-readable part, which is on device
/dev/disk4s1s2. As you can see, this part is only 50 MiB, which is less than the 266 MiB that we’re expecting. If you check which devices actually exist in
/dev/, you’ll find
/dev/disk4 /dev/disk4s1 /dev/disk4s1s2
The one you have to use here is
/dev/disk4s1. This one contains the proper file system of the whole CD.
In general, if you see something like
/dev/disk4in the output of
df -h, that’s what you should use. If you see something like
/dev/disk4s1s2, you’ll most likely have to go with
Create the ISO file
$ cat /dev/disk4s1 > file.iso
You may get this error message:
cat: /dev/disk4s1: Resource busy
If you do, use the following command:
diskutil unmountDisk /dev/disk4s1
Disk /dev/disk4s1 unmounted
Test the ISO image by mounting the new file (or open with Finder):
$ hdiutil attach file.iso