[syslinux] Syslinux DOS-based installer in FreeDOS

[Gene Cumm]

On Fri, May 23, 2014 at 8:29 AM, Ady <ady-sf at hotmail.com> wrote:
> Testing the DOS-based Syslinux installer, syslinux.com, with the "-m"
> parameter, I found that it works as expected under MS-DOS and its DOS
> variants, but it seems to fail under FreeDOS (please correct me if
> I'm wrong).

This sounds like either a bug in FreeDOS or another undesirable
negative interaction.

I vaguely recall FreeDOS having some sort of HDD-acceleration
(caching/prefetching).  A quick Google returns "lbacache" and
"uide.sys".  If so, a test should be run without either running.

> Using FreeDOS kernel v.2041 (386f32), Syslinux v.6.03-pre11 and
> either FAT16 or FAT32 partitions, executing:
>  syslinux.com -m -i c:
>
> or:
>  syslinux.com -f -m -i c:
>
> will not write to the MBR, and will ruin the VBR.
>
> To be clear, the "-m" parameter overwrites parts of the VBR.
>
> If, *instead*, I use the same versions with the command:
>
>  syslinux.com -i c:
>
> (without the "-m" parameter, optionally with "-f" if needed) then it
> works correctly, installing SYSLINUX on the VBR.
>
> Unfortunately, once the "-m" parameter is used, repairing the VBR
> seems to be not so simple as executing the command again without the
> "-m" parameter. Additional tests might be needed so to find out the
> reason.

This is expected as the VBR is now technically corrupt and you'll need
the backup VBR if present.

> I have not tested what would happen if I avoid using "-i". I don't
> know if it would make any difference.

It should balk with an error and refuse to do anything since there's
no action specified (install regardless or upgrade only if
SYSLINUX/EXTLINUX already exists).

> Several combinations of different versions of FreeDOS with different
> versions of Syslinux have not provided better results (in fact, in
> some cases they were worse).
>
> I admit it is also possible that I am making some mistake. I would
> appreciate if someone could try to replicate this behavior.

Your test sound valid to me.

> I hope syslinux.com can be improved so to make it more compatible
> with FreeDOS, not just with MS-DOS.

-- 
-Gene