isohybrid identification

[SamK]

Is there a command that will identify and report that an ISO has been produced via the syslinux isohybrid program?
   

[curaga]

Not that I know of. File sees them as isos. "qemu -hda /path/to/iso" will tell the difference though

[Rich]

Hi SamK
If I understand it correctly, an ISOhybrid basically just has a MBR added to it. Try the following:

Code: [Select]

hexdump -n 2 -s 510 -x -v filename.isoIf I'm correct, a standard ISO will return

00001fe    0000                                                       
0000200

while an ISOhybrid should return

00001fe    aa55                                                       
0000200

If that's the case, couple that with  grep  and you'll probably have what you are looking for.

[SamK]

Hi Rich
Thanks for the idea.

If I understand it correctly, an ISOhybrid basically just has a MBR added to it.

I have looked a ISOhybrid only superficially.  On a test ISO I created the following was observed:

ISO - Pre ISOhybrid
Size reported by the ls command=29,126,656

ISO - Post ISOhybrid
Size reported by the ls command=29,360,128

Perhaps there is something else going on in addition to the MBR?


I have decided against pursuing ISOhybrid at this time. 

The principal reason for this is the way in which mnttool reports it.  The attached screen shot was taken on a machine booted from a USB flash drive created from Multicore v4.0.2 as the Core team produced it in ISOhybrid form.  The USB drive is sdc.  Both sdc and sdc1 are displayed by mnttool.  Either may be mounted independently, but both cannot be mounted concurrently.

For the purpose I had in mind, these may lead to confusion, hence a non ISOhybrid ISO will be used.

[Rich]

Hi SamK
At least satisfy my curiosity and tell me if the hexdump command produced the expected results.

Perhaps there is something else going on in addition to the MBR?

I seem to remember reading something about one of the formats being able to boot from a partition
and the other requiring a drive.

[SamK]

At least satisfy my curiosity and tell me if the hexdump command produced the expected results.

OK - the ISO was created as bootable...

Pre ISOhybrid
hexdump -n 2 -s 510 -x -v name.iso
00001fe    aa55                                                       
0000200


Post ISOhybrid
hexdump -n 2 -s 510 -x -v name.iso
00001fe    aa55                                                       
0000200

I seem to remember reading something about one of the formats being able to boot from a partition and the other requiring a drive.

I tried specifying the --entry parameter of isohybrid as 1 but the mnttool matter remains unchanged.

Time to move on...
   

[curaga]

I got an email saying fdisk works to identify these - indeed, "fdisk -l tinycore.iso" works.

Thanks to Michael Shigorin.

[SamK]

I got an email saying fdisk works to identify these - indeed, "fdisk -l tinycore.iso" works.

Thanks to Michael Shigorin.

So it does - thanks it's handy to know.