How to change volume label of an ISO image without adding a new session?

I am trying to change the volume label (volid) of an ISO9660 disc image file. I could do so manually in a HEX editor, but it would be more convenient to do it from a command-line tool.

What I have tried:

# create image file
xorriso -volid "old volume id" -dev example.iso  -map example_folder/ /
# change volume label
xorriso -volid "new volume id" -dev example.iso

This changes the volume ID but also adds a new session at the end. This obviously makes sense on write-once media, but how do I change the volume label of an ISO image file without adding new data at the end?

I don't know if that is an "officially" supported operation, but if you can do it with a hex editor you can do that programmatically too. Just do the same steps (using your preferred language).

Fun question. I am a sucker for using dd to edit files, so lets do that. I had to look up the spec for the iso9660 format here: https://wiki.osdev.org/ISO_9660 in the section Primary Volume Descriptor.

I have a Slitaz iso sitting in downloads so thats what I will use for an example. This is the iso-info beforehand.

> iso-info slitaz-rolling.iso                                                                              
                                             
iso-info version 2.3.0 x86_64-pc-linux-gnu
Copyright (c) 2003-2005, 2007-2008, 2011-2015, 2017, 2025 R. Bernstein
This is free software; see the source for copying conditions.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE.
__________________________________
ISO 9660 image: slitaz-rolling.iso
Application : tazlito 537/genisoimage 1.1.11 (Linux)
Preparer    : root
Publisher   : www.slitaz.org
System      : LINUX
Volume      : SliTaz core-4in1
Volume Set  : SliTaz cooking
No Joliet extensions

Verify the current info at the correct offset:

> xxd -s 0x8028 -l 32 slitaz-rolling.iso                                                                                                                
00008028: 536c 6954 617a 2063 6f72 652d 3469 6e31  SliTaz core-4in1
00008038: 2020 2020 2020 2020 2020 2020 2020 2020

Change it with disk destroyer and check the change.

> echo "my string of 32 bytes           " | dd of=slitaz-rolling.iso bs=1 seek=32808 count=32 conv=notrunc                                              
32+0 records in
32+0 records out
32 bytes copied, 0.000227785 s, 140 kB/s

> xxd -s 0x8028 -l 32 slitaz-rolling.iso                                                                                                                
00008028: 6d79 2073 7472 696e 6720 6f66 2033 3220  my string of 32 
00008038: 6279 7465 7320 2020 2020 2020 2020 2020  bytes 

>iso-info slitaz-rolling.iso                                                                                                                           iso-info version 2.3.0 x86_64-pc-linux-gnu
Copyright (c) 2003-2005, 2007-2008, 2011-2015, 2017, 2025 R. Bernstein
This is free software; see the source for copying conditions.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE.
__________________________________
ISO 9660 image: slitaz-rolling.iso
Application : tazlito 537/genisoimage 1.1.11 (Linux)
Preparer    : root
Publisher   : www.slitaz.org
System      : LINUX
Volume      : my string of 32 bytes
Volume Set  : SliTaz cooking
No Joliet extensions