[gPXE] 512MB Limitation of gPXE ?

[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.

On Oct 18, 2012, at 22:29, "Shao Miller" <sha0.miller at gmail.com> wrote:

> 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. 
>