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Booting

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barry at isscp

Jan 24, 2008, 11:10 AM

Post #1 of 10 (2888 views)
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Booting

Hi All

My first experience with syslinux I have created a debian live bootable
environment.
Which creates a fat16 format USB-HDD and then uses syslinux to boot up
with (Provided the hardware allows you to boot from USB).

When I plug the USB Stick into say a windows machine it mounts the USB
drive and you can see the linux kernel files syslinux and other files

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)

Thank You

Barry

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hpa at zytor

Jan 24, 2008, 11:38 AM

Post #2 of 10 (2742 views)
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Re: Booting [In reply to]

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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barry at isscp

Jan 24, 2008, 3:29 PM

Post #3 of 10 (2738 views)
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Re: Booting [In reply to]

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
>
> _______________________________________________
> SYSLINUX mailing list
> Submissions to SYSLINUX [at] zytor
> Unsubscribe or set options at:
> http://www.zytor.com/mailman/listinfo/syslinux
> Please do not send private replies to mailing list traffic.
>
>

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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jalifrangis at authenticlick

Jan 24, 2008, 3:40 PM

Post #4 of 10 (2738 views)
Permalink

Re: Booting [In reply to]

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 [mailto:syslinux-bounces [at] zytor] 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
>
> _______________________________________________
> SYSLINUX mailing list
> Submissions to SYSLINUX [at] zytor
> Unsubscribe or set options at:
> http://www.zytor.com/mailman/listinfo/syslinux
> Please do not send private replies to mailing list traffic.
>
>

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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hpa at zytor

Jan 24, 2008, 5:27 PM

Post #5 of 10 (2741 views)
Permalink

Re: Booting [In reply to]

Jacob Alifrangis wrote:
> 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.
>

Actually, 3.60 introduced persistent storage for extlinux, which could
be used for this purpose. It is currently missing installer support for
syslinux, but the core module support is there.

But yes, you need to set the bios boot order to boot from whatever
medium actually has syslinux on it.

-hpa

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murali at google

Jan 25, 2008, 3:44 AM

Post #6 of 10 (2737 views)
Permalink

Re: Booting [In reply to]

On Jan 25, 2008 6:57 AM, H. Peter Anvin <hpa [at] zytor> wrote:
> Jacob Alifrangis wrote:
> > 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.
> >
>
> Actually, 3.60 introduced persistent storage for extlinux, which could
> be used for this purpose. It is currently missing installer support for
> syslinux, but the core module support is there.

For ISOLinux and PXELinux, one might be able to get away with using
the *later sectors* in Track 0 (after leaving space for the MBR) on
the first hard disk. Of course, this assumes that the "first hard
disk" remains the same across boots and that various disk formatting
utilities dont touch that area.

My "autoboot.c32" does that and I found that the assumptions seemed to be true!

>
> But yes, you need to set the bios boot order to boot from whatever
> medium actually has syslinux on it.
>
>
> -hpa
>
> _______________________________________________
> SYSLINUX mailing list
> Submissions to SYSLINUX [at] zytor
> Unsubscribe or set options at:
> http://www.zytor.com/mailman/listinfo/syslinux
> Please do not send private replies to mailing list traffic.
>
>

--
Murali

கற்றது ைகமண் அளவு, கல்லாதது உலகளவு
(What we know is only a handful, what we dont is the rest of the world)
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hpa at zytor

Jan 25, 2008, 7:30 AM

Post #7 of 10 (2749 views)
Permalink

Re: Booting [In reply to]

Murali (முரளி கணபதி) wrote:
>>>
>> Actually, 3.60 introduced persistent storage for extlinux, which could
>> be used for this purpose. It is currently missing installer support for
>> syslinux, but the core module support is there.
>
> For ISOLinux and PXELinux, one might be able to get away with using
> the *later sectors* in Track 0 (after leaving space for the MBR) on
> the first hard disk. Of course, this assumes that the "first hard
> disk" remains the same across boots and that various disk formatting
> utilities dont touch that area.
>
> My "autoboot.c32" does that and I found that the assumptions seemed to be true!
>
>> But yes, you need to set the bios boot order to boot from whatever
>> medium actually has syslinux on it.
>>

It's by and large true for MS-DOS partition tables (although something
else can use it...) However, for non-MS-DOS partition tables it could
be worse.

-hpa

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jalifrangis at authenticlick

Jan 25, 2008, 1:53 PM

Post #8 of 10 (2759 views)
Permalink

Re: Booting [In reply to]

I believe that doing this on a GPT formatted disk could totally zap the partitions, ESPECIALLY in hybrid mode.

-----Original Message-----
From: syslinux-bounces [at] zytor [mailto:syslinux-bounces [at] zytor] On Behalf Of H. Peter Anvin
Sent: Friday, January 25, 2008 7:31 AM
To: For discussion of SYSLINUX and tftp-hpa
Subject: Re: [syslinux] Booting

Murali (முரளி கணபதி) wrote:
>>>
>> Actually, 3.60 introduced persistent storage for extlinux, which could
>> be used for this purpose. It is currently missing installer support for
>> syslinux, but the core module support is there.
>
> For ISOLinux and PXELinux, one might be able to get away with using
> the *later sectors* in Track 0 (after leaving space for the MBR) on
> the first hard disk. Of course, this assumes that the "first hard
> disk" remains the same across boots and that various disk formatting
> utilities dont touch that area.
>
> My "autoboot.c32" does that and I found that the assumptions seemed to be true!
>
>> But yes, you need to set the bios boot order to boot from whatever
>> medium actually has syslinux on it.
>>

It's by and large true for MS-DOS partition tables (although something
else can use it...) However, for non-MS-DOS partition tables it could
be worse.

-hpa

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_______________________________________________
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hpa at zytor

Jan 25, 2008, 2:35 PM

Post #9 of 10 (2733 views)
Permalink

Re: Booting [In reply to]

Jacob Alifrangis wrote:
> I believe that doing this on a GPT formatted disk could totally zap the partitions, ESPECIALLY in hybrid mode.
>
> -----Original Message-----
> From: syslinux-bounces [at] zytor [mailto:syslinux-bounces [at] zytor] On Behalf Of H. Peter Anvin
> Sent: Friday, January 25, 2008 7:31 AM
> To: For discussion of SYSLINUX and tftp-hpa
> Subject: Re: [syslinux] Booting
>
> Murali (முரளி கணபதி) wrote:
>>> Actually, 3.60 introduced persistent storage for extlinux, which could
>>> be used for this purpose. It is currently missing installer support for
>>> syslinux, but the core module support is there.
>> For ISOLinux and PXELinux, one might be able to get away with using
>> the *later sectors* in Track 0 (after leaving space for the MBR) on
>> the first hard disk. Of course, this assumes that the "first hard
>> disk" remains the same across boots and that various disk formatting
>> utilities dont touch that area.
>>
>> My "autoboot.c32" does that and I found that the assumptions seemed to be true!
>>
>>> But yes, you need to set the bios boot order to boot from whatever
>>> medium actually has syslinux on it.
>>>
>
> It's by and large true for MS-DOS partition tables (although something
> else can use it...) However, for non-MS-DOS partition tables it could
> be worse.
>

Yes. I'm considering having an option to do this, but it would have to
be explicitly configured.

-hpa

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jalifrangis at authenticlick

Jan 25, 2008, 2:54 PM

Post #10 of 10 (2750 views)
Permalink

Re: Booting [In reply to]

Also, there NEEDS to some logic to detect which mode the drive is in, so a GPT Disk could never be written to as an MBR Disk etc.

-----Original Message-----
From: syslinux-bounces [at] zytor [mailto:syslinux-bounces [at] zytor] On Behalf Of H. Peter Anvin
Sent: Friday, January 25, 2008 2:36 PM
To: For discussion of SYSLINUX and tftp-hpa
Subject: Re: [syslinux] Booting

Jacob Alifrangis wrote:
> I believe that doing this on a GPT formatted disk could totally zap the partitions, ESPECIALLY in hybrid mode.
>
> -----Original Message-----
> From: syslinux-bounces [at] zytor [mailto:syslinux-bounces [at] zytor] On Behalf Of H. Peter Anvin
> Sent: Friday, January 25, 2008 7:31 AM
> To: For discussion of SYSLINUX and tftp-hpa
> Subject: Re: [syslinux] Booting
>
> Murali (முரளி கணபதி) wrote:
>>> Actually, 3.60 introduced persistent storage for extlinux, which could
>>> be used for this purpose. It is currently missing installer support for
>>> syslinux, but the core module support is there.
>> For ISOLinux and PXELinux, one might be able to get away with using
>> the *later sectors* in Track 0 (after leaving space for the MBR) on
>> the first hard disk. Of course, this assumes that the "first hard
>> disk" remains the same across boots and that various disk formatting
>> utilities dont touch that area.
>>
>> My "autoboot.c32" does that and I found that the assumptions seemed to be true!
>>
>>> But yes, you need to set the bios boot order to boot from whatever
>>> medium actually has syslinux on it.
>>>
>
> It's by and large true for MS-DOS partition tables (although something
> else can use it...) However, for non-MS-DOS partition tables it could
> be worse.
>

Yes. I'm considering having an option to do this, but it would have to
be explicitly configured.

-hpa

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