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

[H. Peter Anvin]

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.