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Re: "wireless" clients

On Sun, 7 May 2006 18:53:08 +0900 (JST) nigel barker wrote:

> > The LTSP pcmcia floppy works around this by putting together a
> > plain old
> >floppy bootloader, a linux kernel, some pcmcia NIC drivers, the
> >pcmcia helper daemon, and some LTSP-specific boot scripts.
> >
> > To get something similar (or wireless) working with current LTSP,
> >anup-to-date 2.6 kernel and related drivers and scripts need to be
> >put
> together.
> I don't understand this part. Surely the purpose of the boot floppy
> is to get pcmcia and NIC up and running? Then the real kernel gets
> loaded. So the reason the old boot floppy no longer works is because
> some things its looking for are no longer located in the same places.
> This ought to be fixable, isn't it?

You snipped what the floppy works around:

> All three are "boot protocols", providing access to a bootloader
> through the network.

Booting into Linux on x86 hardware goes roughly like this:

BIOS -> bootloader -> Linux kernel -> ( initrd -> ) init

PXE, RPL and netboot are all just ways to go from BIOS to bootloader
(or in the case of netboot you can chainload and go from one
bootloader to another).

LTSP floppy does all above steps - which then makes it quite inflexible
about the environment to load afterwards, since the init and rootfs is
on the floppy, not loaded off the network.

Problem with pcmcia (and wireless too) is that PXE can only get youa
single step, so even if the BIOS knows how to activate the NIC to start
a PXE client process, the kernel still needs to access it as well. Linux
needs userspace helper daemons to handle pcmcia and wireless, and they
are normally available only on the final rootfs, _after_ the init has

Hope that clarifies :-)

 - Jonas

* Jonas Smedegaard - idealist og Internet-arkitekt
* Tlf.: +45 40843136  Website: http://dr.jones.dk/

 - Enden er n_r: http://www.shibumi.org/eoti.htm

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