[gPXE] [Etherboot-discuss] how big an image downloaded and booted by gPXE could be?

[Luca]

Thanks a lot.
 Something is still not clear to me though. I'm using gPXE on a diskless
workstation. I use gPXE to download a small ramdisk. Then I use this one to
do a secondary download of the remaining contents.
After the download I can do a pivot_root and switch to the new filesystem.

Yet the space I have left is 1.5G (since I'm doing first download with gPXE
and the image can't be bigger than 1.5GB).

I'm sure I'm missing something, but having everything in RAM, after I
download a small ramdisk with gPXE, where do I save the content of the
secondary download (which is going to be around 4G)?

Thanks,
 Luca

On Fri, Dec 11, 2009 at 10:37 AM, H. Peter Anvin <hpa at zytor.com> wrote:

> On 12/11/2009 07:28 AM, Luca wrote:
> > Thank you. So gPXE can address 4GB of RAM.
> >
> > Then, if I gPXE boot with the following script
> >
> > #!gpxe
> >
> >   kernel https://192.168.1.189/vmlinuz root=/dev/ram0 init=linuxrc
> >   initrd https://192.168.1.189/ramdisk.img
> >   boot
> >
> > the ramdisk's size could not exceed 2G (considering gPXE has to download
> > it and then load it in memory)?
> >
>
> Something like that.  In practice it is probably closer to 1-1.5 GB.
>
> You also don't want to actually use a ramdisk -- initramfs is a *lot*
> more efficient.
>
> However, realistically you probably don't want to do that.  Instead you
> want to bring up a reasonably small ramdisk that contains the contents
> needed to do a secondary download of the remaining contents.  The
> reasons are very simple: no need to double buffer, Linux has a *much*
> more advanced IP stack that gPXE (for, I hope, obvious reasons -- not
> picking on gPXE here), and no 4 GB limitation.
>
> As such, you should get much better preformace that way, and when you're
> talking gigabytes, that matters.
>
>        -hpa
>
> --
> H. Peter Anvin, Intel Open Source Technology Center
> I work for Intel.  I don't speak on their behalf.
>
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