[syslinux] PXELinux question

Gene Cumm gene.cumm at gmail.com
Tue Oct 26 17:44:48 PDT 2010

On Fri, Oct 1, 2010 at 19:08, Anton Aylward <anton.aylward at rogers.com> wrote:
> Yes, I know, this should be in the wiki ...
> I have a couple of laptops that won't boot off USB - no bios capability.

for starters.  This might be the easiest route.  Use a CD to boot PLoP
then use PLoP to boot from your USB drive.

> I have PXELinux serving OK, DHCP and TFTP work fine
> I have a number of ISO images on the server and on a USB stick.
> The USB stick is also bootable - it has a copy of grub.
> I am confused about menu writing.  I see what is there and how what is
> there works, but I can't imagine how to write an entry to do smethng
> like I have in the grub menu ...
> ubuntu Live 9.10" {
>  loopback loop /ubuntu-9.10-desktop-i386.iso
>  linux (loop)/casper/vmlinuz boot=casper
> iso-scan/filename=/ubuntu-9.10-desktop-i386.iso splash --
>  initrd (loop)/casper/initrd.lz
> }
> Grub is pretty capable itself :-)  But its not PXELinux :-)

This looks like Grub opens the ISO, grabs a kernel, an initrd and
possibly throws an extra option in to instruct the initrd that the
live CD itself is an ISO file somewhere in a local file system then

Based on that assessment, you could extract the select boot files
(kernel, initrd, etc) from the ISO and put them on the TFTP then boot
with the USB attached using something like:
LABEL live-9.10
  MENU LABEL Live 9.10"
  LINUX vmlinuz
  INITRD initrd.lz
  APPEND boot=casper iso-scan/filename=/ubuntu-9.10-desktop-i386.iso splash --

MEMDISK is another alternative but won't give the results you want.

The problem is that if you tried to use MEMDISK, you probably won't
have enough RAM to load the whole ISO and use it (at least 1 - 1.5
GiB; 700 + running system) based on the fact that you don't have USB
boot on these laptops.  With either way, once the kernel takes over
PXELINUX and MEMDISK are essentially gone from memory so you'll still
need other local media to load the rest of the filesystem.

Another alternative is to look at BKO (http://boot.kernel.org).  I
think 9.04 is currently up there but it should at least work.


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