Mailing List Archive: chain.c32 question

chain.c32 question

Aug 29, 2007, 1:06 AM

Post #1 of 4 (8636 views)

I'd like to use chain.c32 to allow the computer boot from HARDDISK if
needed.

If I use isolinux and boot from CD, the following works OK:
chain.c32 hd0

But if I boot from USB Flash Key, it sometimes work and sometimes it
doesn't and I have to use
chain.c32 hd1
(it seems BIOS assigns hd0 to the flash key sometimes, so the real
harddisk is hd1 in that case).

Is there any way to tell chain.c32 to SKIP the device chain.c32 is
running from? So it will skip hd0 here and proceed the next harddisk. Or
is there any other solution, except the one to create two menu entries
in syslinux.cfg with "boot from C: and boot from D:" ?

Thank you

Tomas M

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Re: chain.c32 question [ In reply to ]

hpa at zytor

Aug 29, 2007, 1:08 AM

Post #2 of 4 (8359 views)

Permalink

Tomas M wrote:
> I'd like to use chain.c32 to allow the computer boot from HARDDISK if
> needed.
>
> If I use isolinux and boot from CD, the following works OK:
> chain.c32 hd0
>
> But if I boot from USB Flash Key, it sometimes work and sometimes it
> doesn't and I have to use
> chain.c32 hd1
> (it seems BIOS assigns hd0 to the flash key sometimes, so the real
> harddisk is hd1 in that case).
>
> Is there any way to tell chain.c32 to SKIP the device chain.c32 is
> running from? So it will skip hd0 here and proceed the next harddisk. Or
> is there any other solution, except the one to create two menu entries
> in syslinux.cfg with "boot from C: and boot from D:" ?
>

In the 3.52-preX series you can tell it to chainload by MBR signature
(bytes 440-443 in the MBR.) However, you might have problems booting
your other operating system from the second hard disk.

-hpa

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Re: chain.c32 question [ In reply to ]

xl at xlsigned

Aug 29, 2007, 1:39 AM

Post #3 of 4 (8374 views)

Permalink

Quoting "H. Peter Anvin" <hpa@zytor.com>:

> Tomas M wrote:
> > I'd like to use chain.c32 to allow the computer boot from HARDDISK if
> > needed.
> >
> > If I use isolinux and boot from CD, the following works OK:
> > chain.c32 hd0
> >
> > But if I boot from USB Flash Key, it sometimes work and sometimes it
> > doesn't and I have to use
> > chain.c32 hd1
> > (it seems BIOS assigns hd0 to the flash key sometimes, so the real
> > harddisk is hd1 in that case).
> >
> > Is there any way to tell chain.c32 to SKIP the device chain.c32 is
> > running from? So it will skip hd0 here and proceed the next harddisk. Or
> > is there any other solution, except the one to create two menu entries
> > in syslinux.cfg with "boot from C: and boot from D:" ?
> >
>
> In the 3.52-preX series you can tell it to chainload by MBR signature
> (bytes 440-443 in the MBR.) However, you might have problems booting
> your other operating system from the second hard disk.
>
> -hpa

grub has a "map" command that allows to swap order of BIOS drives.
Would it be possible to have such a command in syslinux?
Like this ...

SWAPDRIVES
LOCALBOOT 0

Axel

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Re: chain.c32 question [ In reply to ]

tomas at slax

Aug 29, 2007, 2:27 AM

Post #4 of 4 (8367 views)

Permalink

> In the 3.52-preX series you can tell it to chainload by MBR signature
> (bytes 440-443 in the MBR.) However, you might have problems booting
> your other operating system from the second hard disk.
>

I think this is not what I need, because I can never know what is the
MBR signature of the C: drive on the user's computer. Or do all the
windowses use the same serial?

But here is another idea: I can perhaps know the MBR signature of my
syslinux-booting USB Flash Key! :) So if I could tell chain.c32 to try
all disks and load the first one which _doesn't_ have a specific
signature, it would help me more I guess.

Tomas M

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