[syslinux] Booting

[Jacob Alifrangis]

The boot loader on the Windows CD detects whether there is a partition
located on device 0x80 (First BIOS Harddrive), if it does not see one,
it boots from CD first, if it does it just asks you to "Press Any Key"

The logic you are looking for doesn't exist on PCs,

There isn't a firmware variable that is accessible from modern Operating
Systems, especially not one that survives a reboot.

What you are looking to do, can be accomplished from a Com32 Module
though, but you'll still need to set the bios Boot Order manually to
always boot from USB (Which is exceedingly dangerous and insecure)

Your best bet to accomplish this, is writing a state-file to the
harddrive on the boot partition(Must be 0x80h - 0x83h) or syslinux would
never see it, then you must write a com32 module for NTFS and FAT /
Fat32 so you can read the state-file, and finally act on it via an "If"
statement, something that syslinux doesn't support either yet.


Good luck, if you find a way around it, lemme know.

-----Original Message-----
From: syslinux-bounces at zytor.com [mailto:syslinux-bounces at zytor.com] On
Behalf Of Barry Fawthrop
Sent: Thursday, January 24, 2008 3:29 PM
To: For discussion of SYSLINUX and tftp-hpa
Subject: Re: [syslinux] Booting

H. Peter Anvin wrote:
> Barry Fawthrop wrote:
>   
>> Question: Is there a way to click a file or exe, which will cause the

>> machine to reboot pointing to the USB stick (which is already
inserted)
>> without:
>>    (a) effecting or modifing the MBR
>>    (b) or the HDD?
>>
>> Some hardware
>>   (1) Will boot from USB no problems
>>   (2) Some you have to change the BIOS order
>>   (3) Others don't know what USB booting is  (TO overcome this)
>>
>> In sequence in mind:
>> Running Windows,
>> Insert the USB stick,
>> Change to F: (or whatever USB stick is)
>> Click a reboot file
>> reboot the machine into the USB stick
>> Work in the USB environment
>> shutdown, removed the USB stick
>> boot back into Windows (totally uneffected)
>>
>> How is this possible? (I'm willing to write my own reboot.exe if it
does 
>> not exist already)
>>
>>     
>
> It's not possible except with older versions (95/98/ME) of Windows 
> (where you could use Loadlin) or by using a virtual machine.
>
> 	-hpa
>
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>   

Hi Peter
Thank you for your response
I'm very  keen to understand the whole boot process better
What stops a 2000/XP/ machine?
I know when you install XP (for example)
Phase 1: Your boot the CD (Press any key to boot from CD) and it install

part 1

Phase 2: Then it reboots and automatically continues
     (even though the CD is in, and does not ask if you want to boot 
from CD)
It continues and then says, please remove all CDs and reboot after part
2

How does it get the end of  part 1 phase 2 right?
Surely it must write to memory or  something, that bypasses bios normal 
order
And then removes this during phase 2 ?
If this makes sense?

Thanks
Barry

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