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Re: custom Debian installation ISO image


Summary in advance:

The ISO 9660 image aspects seem to be ok. Somehow the VM
or the booted kernel decide that the emulated CD-ROM has
only 500 MiB of read capacity.

The imaginable information sources of size in the image file
- isohybrid MBR partition size
- ISO 9660 Volume Space Size
- storage size of the image file
None of them is supposed to tell 500 MiB here.

> Erm... 548405248 / 1024000 = 535.552

So the error message count is probably in blocks of 512 bytes.
This would mean your image is perceived 47104 such blocks too
short (548405248 / 512 - 1024000). More than 20 MB.

>From where does the VM get the number 1024000 ?
500 MiB is too small for a legacy limit of CD size.

isohybrid MBR partition size:
What do you get from

  /sbin/fdisk -lu ...your.iso.image...

ISO 9660 Volume Space Size:
What do you get from

  xorriso -indev ...your.iso.image... -toc

Experiment proposals:

What happens if you reduce the size of your image below 500 MiB ?

What happens if you try to boot a Debian netinst image ?

> But omitting isohybrid will make this image unbootable from USB?

Yes. But if it works with the VM, then we know that the MBR
is involved.

> The last file starts on 267309.
> 267309 * 2048 = 547448832 (still less than ISO)

The column after the block address tells the number of blocks.
It should be not more than 467, then. (Probably we have some
padding at the end. So it should be less. 317 perhaps ?)


> [xorriso version is] Debian sid's 1.2.2-2.

Deplorably old.
But the ChangeLog since then does not list a bug that could be
blamed for such a fat misperception by the VM or the kernel.

Have a nice day :)


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