Syslinux - Jun 2008 - Syslinux boot from a partition on sub stick with GPT label

I recently tried to install several distros on a usb stick, with the
peculiarity of creating in it a GPT label rather than the usual dos label.
Installed Grub2 using the parted bios_grub flag on a partition, I proceeded
to copy several distros on the remaining partitions.
Grub2 worked fine, chainloading syslinux on each of the partitions. Or
rather it worked all fine until I reached the fifth partition. Once tried
with that all I got was a boot error.
Having tried extlinux on that one I persisted thinking that might have been
the source of the problem. So I duplicated the contents of the fourth
partition, installing syslinux as with that one.
Boot error, again and again.
The fact that the first four paritions work as expected sounds suspiciously
related to a situation involving the use of a dos label to me. Could anyone
explain to me where the problem lies:
with syslinux and gpt, with grub2 and gpt or somewhere else?
Thanks in advance and forgive me should I have wandered off-topic.

Fulvio Scapin

Fulvio Scapin wrote:
> I recently tried to install several distros on a usb stick, with the
> peculiarity of creating in it a GPT label rather than the usual dos label.
> Installed Grub2 using the parted bios_grub flag on a partition, I proceeded
> to copy several distros on the remaining partitions.
> Grub2 worked fine, chainloading syslinux on each of the partitions. Or
> rather it worked all fine until I reached the fifth partition. Once tried
> with that all I got was a boot error.
> Having tried extlinux on that one I persisted thinking that might have been
> the source of the problem. So I duplicated the contents of the fourth
> partition, installing syslinux as with that one.
> Boot error, again and again.
> The fact that the first four paritions work as expected sounds suspiciously
> related to a situation involving the use of a dos label to me. Could anyone
> explain to me where the problem lies:
> with syslinux and gpt, with grub2 and gpt or somewhere else?
> Thanks in advance and forgive me should I have wandered off-topic.
Syslinux doesn't read the partition table *at all*, so the only way this 
could have happened is that Grub2 passed it broken partition offset 
information.

Last I checked, Grub did indeed pass broken partition information for 
partitions past the fourth one when used with a DOS partition table.

For what it's worth, there is a GPT-aware MBR included with the syslinux 
prereleases.  However, you will have to manually set the bootable 
partition with a hex editor, I'm afraid.  Also, I don't yet have support
for GPT in chain.c32 for chainloading other systems - this probably 
would be a good thing to do.

	-hpa

Hallo, Fulvio,

Du (trantorvega) meintest am 21.06.08:
> Grub2 worked fine, chainloading syslinux on each of the
> partitions. Or rather it worked all fine until I reached the fifth
> partition. Once tried with that all I got was a boot error.
> The fact that the first four paritions work as expected sounds
> suspiciously related to a situation involving the use of a dos label
> to me.
One of the four primary partitions must be an extended partition if you  
want to use partition 5 (or higher).

Viele Gruesse!
Helmut

Indeed. But that's what's needed with a dos label. I chose a GPT label
to avoid that, among other reasons. There are no extended partitions under GPT.

-----Original Message-----
From: "Helmut Hullen" <Hullen at t-online.de>
Date: Saturday, giu 21, 2008 8:08 am
Subject: Re: [syslinux] Syslinux boot from a partition on sub stick with GPT 
label
To: syslinux at zytor.comReply-To: For discussion of SYSLINUX and tftp-hpa
<syslinux at zytor.com>

Hallo, Fulvio,

Du (trantorvega) meintest am 21.06.08:
> Grub2 worked fine, chainloading syslinux on each of the
 partitions. Or rather it worked all fine until I reached the fifth
 partition. Once tried with that all I got was a boot error.
> The fact that the first four paritions work as expected sounds
 suspiciously related to a situation involving the use of a dos label
 to me.

One of the four primary partitions must be an extended partition if you  
want to use partition 5 (or higher).

Viele Gruesse!
Helmut