Extracting floppy boot image from ISO with dd?

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ol5

Member
Sep 17, 2020
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0
I know there are utilities that can extract the boot image from a CD ISO which can then be used to create a boot floppy or another bootable CD ISO. Anyone know if the differences in the boot header for a bootable FreeDOS floppy image, CD ISO or USB ISO is the sector number where the boot code is located? I think for floppies it is located at the first sector on the disk, but I don't know about CD or USB bootable ISOs. If it is just a difference in the sector number, I would think we should be able to use the dd command to extract a floppy image by starting at the correct sector of the CD or USB boot ISO and specify the number of sectors to extract.
 

drwtsn32

Active member
Sep 19, 2020
32
11
I am not sure if you can use dd. The boot "file" may be of varying sizes depending on what type of boot ISO it is.

That being said, on Windows I have used 7-zip to extract the boot file. 7-zip shows it in a special folder called "[BOOT]".
If you install 7-zip on Linux (p7zip-full) you can use the 7z command to extract the file:

Code:
7z e isofile.iso '[BOOT]'

Here I'm extracting it from the ultimate boot CD iso. Note the 2KiB "Boot-NoEmul.img" file.
Capture.PNG
 
Last edited:

ol5

Member
Sep 17, 2020
5
0
It is good to know that option is available in the Linux version. That must be a Linux only option because it was not an option on the Mac and Window versions I have installed. I wonder if it is limited to ony ISOs with Linux boot code.
 

drwtsn32

Active member
Sep 19, 2020
32
11
It is good to know that option is available in the Linux version. That must be a Linux only option because it was not an option on the Mac and Window versions I have installed. I wonder if it is limited to ony ISOs with Linux boot code.
No, this works on 7zip on Windows too. You can extract the boot image with either the 7zip GUI (File Manager) or the command line. Not sure about the Mac though.
 
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drwtsn32

Active member
Sep 19, 2020
32
11
And sorry, I assumed you meant Linux when you were asking about dd. I forget that Mac OS X has most UNIXy commands too!