[gPXE] 512MB Limitation of gPXE ?

[LinuxByExamples]

Hi,

This is the first time I use this mailing list, so I am very sorry if I
have made any mistake.

Well, here is my case, I have followed this post :
http://www.linuxbyexamples.net/2012/08/boot-winxp-from-http-server.html

_ I can use gPXE to download two files : grub.exe and winxp.vhd image by
http. Later, grub.exe will map the vhd image into memory then successfully
load the windows xp. The config file look this :

LABEL gpxelinux
kernel http://192.168.100.254/grub.exe
initrd http://192.168.100.254/MiniXP350.vhd
APPEND --config-file="map (rd)+1 (hd0); map --hook; chainloader
(hd0,0)/ntldr"

This works very well.

_ But when the winxp.vhd image becomes bigger than 512MB ( I added some
more files and winxp modules into to the image), the loading step fire an
error tell me that the image can not be loaded ... I then try put the
bigger vhd image and grub.exe into usb disk and I can boot it well (without
using gPXE http loading). So, I guess the problem is in gPXE module, it
looks like that gPXE can not load the image bigger than 512MB ? is this
right or I have missed something else ?

I hope you can help to overcome this limitation.

Thank you guy.
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[Shao Miller]

Good day, guy.

Your config-file LABEL doesn't seem right. The LABEL should reflect the
name of the item that you are booting. You have already booted gpxelinux.0
and it is gpxelinux.0 that reads the config-file, so "LABEL gpxelinux"
doesn't make a lot of sense. I'd suggest using "LABEL winxp", since that is
what you are booting from gpxelinux.0.

Back to your problem, is there any reason why you are not using MEMDISK,
instead of GRUB4DOS? Please try it and see if there's any difference:

LABEL winxp
KERNEL http://192.168.100.254/memdisk
INITRD http://192.168.100.254/MiniXP350.vhd
APPEND raw

Also note that "Later, grub.exe will map the vhd image into memory" is
incorrect. gpxelinux.0 is the program that maps the VHD into memory in your
current scenario. GRUB4DOS establishes a very simple mapping of BIOS drive
0x80 to the already-mapped VHD image.

Also: Why are you calling your image a VHD? If it can be booted by GRUB4DOS
in the way that you've described, the image is basically just a
sector-by-sector disk image. There's no need to confuse things by calling
it a VHD.

- Shao Miller

________________________________________
From: gpxe-bounces at etherboot.org [mailto:gpxe-bounces at etherboot.org] On
Behalf Of LinuxByExamples
Sent: Thursday, October 18, 2012 09:04
To: gpxe at etherboot.org
Subject: [gPXE] 512MB Limitation of gPXE ?

Hi,?

This is the first time I use this mailing list, so I am very sorry if I have
made any mistake.

Well, here is my case, I have followed this post
:?http://www.linuxbyexamples.net/2012/08/boot-winxp-from-http-server.html

_ I can use gPXE to download two files : grub.exe and winxp.vhd image by
http. Later, grub.exe will map the vhd image into memory then successfully
load the windows xp. The config file look this :

LABEL gpxelinux
kernel http://192.168.100.254/grub.exe
initrd http://192.168.100.254/MiniXP350.vhd
APPEND --config-file="map (rd)+1 (hd0); map --hook; chainloader
(hd0,0)/ntldr"

This works very well.

_ But when the winxp.vhd image becomes bigger than 512MB ( I added some more
files and winxp modules into to the image), the loading step fire an error
tell me that the image can not be loaded ... I then try put the bigger vhd
image and grub.exe into usb disk and I can boot it well (without using gPXE
http loading). So, I guess the problem is in gPXE module, it looks like that
gPXE can not load the image bigger than 512MB ? is this right or I have
missed something else ?

I hope you can help to overcome this limitation.

Thank you guy.?

[LinuxbyExamples]

Hi Shao,

Thanks very much for your reply. It look likes that I have miss-understand a lot thing :)

I call the image vhd because I did use VirtualBox to create the image (preallocated disk in vhd format). This is the term from virtualbox, I just call it as.

I use grub4dos because in the image, winxp has been installed with a special driver called winVblock, and I am not sure if memdisk can work with this drivers ?!

The last thing, so there is no limitation about 512MB with gPXE ?! or I have to use memdisk to overcome this ?!

I will try memdisk and feedback soon.

Brs.

Post by Shao Miller
Good day, guy.
Your config-file LABEL doesn't seem right. The LABEL should reflect the
name of the item that you are booting. You have already booted gpxelinux.0
and it is gpxelinux.0 that reads the config-file, so "LABEL gpxelinux"
doesn't make a lot of sense. I'd suggest using "LABEL winxp", since that is
what you are booting from gpxelinux.0.
Back to your problem, is there any reason why you are not using MEMDISK,
LABEL winxp
KERNEL http://192.168.100.254/memdisk
INITRD http://192.168.100.254/MiniXP350.vhd
APPEND raw
Also note that "Later, grub.exe will map the vhd image into memory" is
incorrect. gpxelinux.0 is the program that maps the VHD into memory in your
current scenario. GRUB4DOS establishes a very simple mapping of BIOS drive
0x80 to the already-mapped VHD image.
Also: Why are you calling your image a VHD? If it can be booted by GRUB4DOS
in the way that you've described, the image is basically just a
sector-by-sector disk image. There's no need to confuse things by calling
it a VHD.
- Shao Miller
________________________________________
From: gpxe-bounces at etherboot.org [mailto:gpxe-bounces at etherboot.org] On
Behalf Of LinuxByExamples
Sent: Thursday, October 18, 2012 09:04
To: gpxe at etherboot.org
Subject: [gPXE] 512MB Limitation of gPXE ?
Hi,
This is the first time I use this mailing list, so I am very sorry if I have
made any mistake.
Well, here is my case, I have followed this post
: http://www.linuxbyexamples.net/2012/08/boot-winxp-from-http-server.html
_ I can use gPXE to download two files : grub.exe and winxp.vhd image by
http. Later, grub.exe will map the vhd image into memory then successfully
LABEL gpxelinux
kernel http://192.168.100.254/grub.exe
initrd http://192.168.100.254/MiniXP350.vhd
APPEND --config-file="map (rd)+1 (hd0); map --hook; chainloader
(hd0,0)/ntldr"
This works very well.
_ But when the winxp.vhd image becomes bigger than 512MB ( I added some more
files and winxp modules into to the image), the loading step fire an error
tell me that the image can not be loaded ... I then try put the bigger vhd
image and grub.exe into usb disk and I can boot it well (without using gPXE
http loading). So, I guess the problem is in gPXE module, it looks like that
gPXE can not load the image bigger than 512MB ? is this right or I have
missed something else ?
I hope you can help to overcome this limitation.
Thank you guy.

[Shao Miller]

You're welcome.

I now understand why you call the disk image a VHD. Thank you for
explaining this, as it helps me to understand why a lot of people call
sector-by-sector disk images VHDs.

WinVBlock works with MEMDISK, so you can skip the GRUB4DOS.

I've suggested MEMDISK because it seems simpler than the GRUB4DOS stuff you
are doing, but also because I am interested in knowing if there's any
difference in gpxelinux.0's behaviour in regards to refusing to load such a
large image into memory.

Please do report back, however, since gpxelinux.0 is { gPXE -> PXELINUX },
this seems more like a PXELINUX question than a gPXE question. It might be
better to e-mail the Syslinux mailing-list, just in case PXELINUX is having
the problem.

- Shao Miller

-----Original Message-----
From: LinuxbyExamples [mailto:linuxbyexamples at gmail.com]
Sent: Thursday, October 18, 2012 19:09
To: Shao Miller
Cc: <gpxe at etherboot.org>
Subject: Re: [gPXE] 512MB Limitation of gPXE ?

Hi Shao,

Thanks very much for your reply. It look likes that I have miss-understand a
lot thing :)

I call the image vhd because I did use VirtualBox to create the image
(preallocated disk in vhd format). This is the term from virtualbox, I just
call it as.

I use grub4dos because in the image, winxp has been installed with a special
driver called winVblock, and I am not sure if memdisk can work with this
drivers ?!

The last thing, so there is no limitation about 512MB with gPXE ?! or I have
to use memdisk to overcome this ?!

I will try memdisk and feedback soon.

Brs.

Post by Shao Miller
Good day, guy.
Your config-file LABEL doesn't seem right. The LABEL should reflect the
name of the item that you are booting. You have already booted

gpxelinux.0

Post by Shao Miller
and it is gpxelinux.0 that reads the config-file, so "LABEL gpxelinux"
doesn't make a lot of sense. I'd suggest using "LABEL winxp", since that

is

Post by Shao Miller
what you are booting from gpxelinux.0.
Back to your problem, is there any reason why you are not using MEMDISK,
LABEL winxp
KERNEL http://192.168.100.254/memdisk
INITRD http://192.168.100.254/MiniXP350.vhd
APPEND raw
Also note that "Later, grub.exe will map the vhd image into memory" is
incorrect. gpxelinux.0 is the program that maps the VHD into memory in

your

Post by Shao Miller
current scenario. GRUB4DOS establishes a very simple mapping of BIOS

drive

Post by Shao Miller
0x80 to the already-mapped VHD image.
Also: Why are you calling your image a VHD? If it can be booted by

GRUB4DOS

Post by Shao Miller
in the way that you've described, the image is basically just a
sector-by-sector disk image. There's no need to confuse things by calling
it a VHD.
- Shao Miller
________________________________________
From: gpxe-bounces at etherboot.org [mailto:gpxe-bounces at etherboot.org] On
Behalf Of LinuxByExamples
Sent: Thursday, October 18, 2012 09:04
To: gpxe at etherboot.org
Subject: [gPXE] 512MB Limitation of gPXE ?
Hi,
This is the first time I use this mailing list, so I am very sorry if I

have

Post by Shao Miller
made any mistake.
Well, here is my case, I have followed this post
: http://www.linuxbyexamples.net/2012/08/boot-winxp-from-http-server.html
_ I can use gPXE to download two files : grub.exe and winxp.vhd image by
http. Later, grub.exe will map the vhd image into memory then successfully
LABEL gpxelinux
kernel http://192.168.100.254/grub.exe
initrd http://192.168.100.254/MiniXP350.vhd
APPEND --config-file="map (rd)+1 (hd0); map --hook; chainloader
(hd0,0)/ntldr"
This works very well.
_ But when the winxp.vhd image becomes bigger than 512MB ( I added some

more

Post by Shao Miller
files and winxp modules into to the image), the loading step fire an error
tell me that the image can not be loaded ... I then try put the bigger vhd
image and grub.exe into usb disk and I can boot it well (without using

gPXE

Post by Shao Miller
http loading). So, I guess the problem is in gPXE module, it looks like

that

Post by Shao Miller
gPXE can not load the image bigger than 512MB ? is this right or I have
missed something else ?
I hope you can help to overcome this limitation.
Thank you guy.