Re: Is initrd enough?`
I'm not sure whether you know of or have considered using the PXE
protocol to boot your client nodes. Most modern Ethernet NICs allow you
to boot off a central server using the TFTP protocol. For smallish
applications you don't really need a hard disk (or cf disk). If you have
bigger space requirements you could potentially NFS mount a shared
directory structure from the central server.
You first assemble a target root filesystem (rootfs) with your OS and
application, which you will eventually package as an initrd image. You
then compile a light-weight kernel according to your needs and ensure
that it has initrd support enabled. Both the kernel and rootfs are shared
from the central controller and each client accesses them from the PXE
environment. Your whole OS exists in RAM and is cleaned on every boot
(you can save files either onto a local cf disk or NFS mount).
If you need more information, search for "TinyGentoo" using Google.
Re: Is initrd enough?`
> I'm not sure whether you know of or have considered using the PXE
> protocol to boot your client nodes.[/color]
Yes I did.
These machines are going to be connected most of the time, and/or in
most installation. They have to be able to boot without net
connectivity as well, though. And their local environment (is there
a server on the same LAN? etc.) is not very well-defined.
So network-boot is not an option for me.
As an update to my oldish post:
Yes, not only is it perfectly acceptable to not switch roots if your
system does not require it. It works, too. And it is not even against
any law :-).
I now have a system that boots from CF using SysLinux. Then loads
an initramfs-image from said CF and uses that as final root-fs. It
then goes on initializing using minit and in that process loads
modules for network and the FAT-filesystem the CF is formatted as.
Finally it mounts said CF again unter /mnt to read per-device
configuration and allow a bit of persistent storage. It is also
possible to update the little thingies in the field by supplying
a fresh kernel and/or initramfs to the mounted FAT-fs over SCP (as
the rootfs-image has been loaded into RAM and is not mounted in
itself) and then reboot them.
I built that system using T2 ([url]http://www.t2-project.org[/url]). Without any
special aggressive tuning measures it is very full-featured based on
a current kernel and weighs in at about 7MB Kernel+gzipped initramfs.
After boot 18MB of RAM are used.
Marian Aldenhövel, Rosenhain 23, 53123 Bonn
"Success is the happy feeling you get between the time you
do something and the time you tell a woman what you did."