[Etherboot-users] Re: [Ltsp-discuss] Questions about pxe and etherboot

[Marty C. <md...@et...>]

On Jan 21, 2006, at 5:10 PM, Richard Bos wrote:

> would you be so kind to get me updated about booting from the net  
> via pxe,
> etherboot and the like.

Hi there.  Perhaps I can be of help.  I created and maintain rom-o- 
matic.net, and am Project Leader for the Etherboot team.

PXE is a method for booting and managing computer via a network  
connection.  Etherboot implements PXE as do various pieces of  
software.  Etherboot didn't used to implement the PXE method of  
booting. Support for PXE was added in the last couple of years.

>     I understand how it works, but I miss the fine
> details to really implement it.  BTW I started to become interested  
> in pxe
> after reading an email exchange between Jim McQuillan and Simon  
> Langley about
> getting notebooks/laptops connected with a wireless pocket access  
> point
> device (wireless bridge) (september last year).   From the wiki I  
> understand
> that the notebook should be booted using pxe.... here my adventure
> (questions) starts ;)

Good questions.  I'm glad you're wondering, and glad you're trying to  
find out.

> Sofar I understand that the etherboot images from rom-o-matic can  
> be used for
> this purpose.

They can be used to boot computers over the network using both PXE  
method and what we'll call the NBI method of network booting.   
Etherboot and PXE methods both use DHCP and TFTP.  Etherboot supports  
some additional protocols, and when using Etherboot's older method of  
booting, the image to be booted is prepared (wrapped) using a tool  
called mknbi (make-network-boot-image).

>   In my case I have succesfully created floppy boot images.  Is
> it now possible (in the client system)  to swap these floppy  
> bootimages for
> networkcard pxe images (by programming an eprom image from rom-o- 
> matic) and
> have the same machine still booted via the network?  I mean is no  
> there no
> bios option that needs to be changed (for example: change boot  
> order.  Make
> lan the first thing to try instead of the floppy disk drive).  As  
> far as I
> remember I have not seen a 'boot from the lan' option in the bioses  
> that I
> have looked at.   Is it like this, that when a pxe image is present  
> in a
> network card, it automatically boots the machine?
> I did not find this explained on this page:
> http://wiki.ltsp.org/twiki/bin/view/Ltsp/PXE hence I my question.

BIOSes have evolved, and have different ways of expressing network  
booting capability.  If you have a reasonably recent Intel  
motherboard, for instance, with a Phoenix BIOS, and you put a NIC  
card in with a PXE boot ROM on it, when you go to the BOOT menu, you  
can actually see the boot ROM as a boot option along with the floppy  
and hard drive, and you can set its order.  This is part of the BIOS  
specification, and if your boot ROM is "PNP Conformant" (and your  
BIOS is), you can set the boot priority of things like Adaptec SCSI  
cards, and Ethernet Cards, and your BIOS will respect it.

Not all BIOSes correctly implement PNP, but quite a few do.  A BIOS  
update in many cases will help. If the BIOS copyright date is in the  
early 1990s, you may have some difficulty, and in that case,  
Etherboot will likely just run.

> For the moment I just assume that pxe boots the system when it is  
> present.
> This is for my next question.  In case a noteboot does not support  
> pxe on its
> own ethernet card (pcmcia card), would the following card make any  
> notebook
> pxe enabled:
> http://www.argontechnology.com/product.aspx/cid1/103/pid/304 ?
> It sounds strange to me, that when a notebook is not aware of pxe  
> on its one
> because it was never designed for it, that it would now  
> automatically work
> when the above mentioned card is plugged in....

   Product Description
   Argon's EP-4103DL-PXE Cardbus Fast Ethernet PC Card with PXE
   10/100 Fast Ethernet Dongle-less PCMCIA
   Complies with IEEE 802.3 10BaseT and 802.3u 100BaseTX Standards
   Supports 10/100M Auto-Negotiation 32bit High Performance 100Mbps  
Networking

   PXE Support included with Argon's PXE on Disk: works with Argon  
Client Management
   Services (CMS) PXE Server or Microsoft Remote Installation  
Services (RIS).

Hmm, I believe that you'll need to boot from their floppy to get PXE  
to work.

The technical reason is that when most notebook boot, unless their  
Ethernet ports are on the motherboard, they have to initialize a PCI  
to PCMCIA bridge chip.

The question is, where is the code to do this?  Well, it kind of has  
to be done by the BIOS, which would then have to know how to control  
whatever PCMCIA Ethernet card you happen to have plugged into your  
PCMCIA slot.

There's the rub.  Unless your laptop BIOS specifically knows what  
bridge chip is being used, and what PCMCIA card is being used, most  
laptops without Ethernet wait for a kernel or other boot code (like  
Argon's PXE on Disk (kind of like an Etherboot floppy)), to do it.

Etherboot, unfortunately doesn't yet know how to deal with PCMCIA  
buses.  It's one of the things we hope to add, but so far, we do PCI  
and ISA buses mainly, which takes care of the majority of cases.   
We'd like to do PCMCIA and USB, and I'm sure we'll get there in time.  
Someone will decide they want it, and do it or fund it, just like PXE  
support.

> I'll highly appreciate any explanation on pxe.  The wiki pages are  
> good, but
> unfortenately they just missed the 2 points mentioned above.

I hope this is helpful.  I think my answers are correct.  I hope and  
expect that someone will correct me if I am mistaken.

> Another question I have (just out of curiousty); what ethercards  
> support pxe
> out the box nowadays all?  Or should they all get an eprom to  
> enable pxe?
> Same question for notebooks, which notebooks support pxe nowadays,  
> is that
> all or for example only the IBM thinkpad (that's the answer from  
> google) ;)

For an Ethernet card to support PXE out of the box, it needs a flash  
EEPROM.  This raises the cost, but not so much as in the old days.  I  
think I noticed an RTL8169 (Gigabit Card) that has PXE on it for not  
too much more than $20 the other day.

Now, if you're a bargain hunter, you can find old Intel EEPRO100s and  
3COM 3C905CTXM cards, which have PXE in flash memory, and will  
network boot by loading PXELINUX.0 from the SYSLINUX/PXELINUX/ 
ISOLINUX package.

Well, hopefully some of that will make sense, and help you on your  
way.  If you need more information, please post to the list.  We're  
here to help.

> TIA

You're welcome.

> Richard Bos
> Without a home the journey is endless

Marty

-- 
     Try: http://rom-o-matic.net/ to make Etherboot images instantly.