[syslinux] isohybrid and ISO images whose size is not a multiple of 2048 bytes vs. VirtualBox

[intrigeri]

Hi,

[not sure if this was answered already.]

Ady via Syslinux wrote (17 Feb 2015 19:16:09 GMT) :
> I don't know whether there is some bug in any one of the isohybrid 
> tools included in Syslinux (there might be). Which one are
> you using? 

We're using the C version, since we're well aware that the Perl one is
currently unmaintained (and back when we've learned about it, we've
actually issued a call for help on our development mailing-list).

We're currently using isohybrid from the Debian's 6.03+dfsg-5 package,
modified in two ways:

  * we've rebuilt it for Debian Wheezy (shouldn't change anything
    relevant here)
  * we're applying two patches from Scot Doyle, that were submitted on
    this mailing-list a while ago, that fix boot on some Chromebooks,
    namely: load_linux-correct-type.patch, and
    relocatable-kernel-loads.patch

For the record, I've verified than neither Debian's patches, nor the
ones we add on top, touch utils/isohybrid.{c,h}.

> Is it part of the same exact version of the ISOLINUX bootloader?

Yes. Since we've been bitten by version incompatibilities when we
migrated from syslinux 4.x to 6.x, we're taking great care to use the
very same version of syslinux for everything. Now, you make me
curious, and I wonder how this can be relevant to the case at hand :)

> Or, perhaps, are you using an external tool (i.e. not using any of
> the ones included in Syslinux)?

Nope. If it were the case, I would have made it extra clear, or more
likely, I would not have bothered you folks about issues with software
you're not distributing nor maintaining :)

> Have you tried not using the Syslinux-related packages, and instead 
> using the upstream official *pre-built* binaries (downloaded from 
> kernel.org) to build a new ISO image and then to make it isohybrid 
> (both pre-built binaries, the isolinux.bin bootloader and the isohybrid 
> tool, from the upstream official archives)?

At least I have not tried this, but it's been clarified later in this
thread that what we're experiencing is fully explained by the way
isohybrid is written.

Cheers,
--
intrigeri