[ILUG] Embedded vs PC version

[Padraig Brady]

Carlos Luna wrote:
> Hello everyone.
> 
> I am very, very new to Linux so if I ask some ignorant questions, I
> apologize in advance.
> 
> I've been thrown onto a project at work which involves a mini PC (Intel chip
> on a miniturized motherboard, RAM, USB port, etc) and have been given the
> task of finding a suitable OS for it.  They want to go with Linux and I see
> no problem with that, since Linux is a very stable environment, according to
> all the Linux-heads I've ever spoken to.  The requirements for this device
> is that it has to be tolerant to being TURNED ON AND OFF from the power
> switch.

sounds familiar :-)

> Question 1: Is a normal distribution of Linux able to handle the possibility
> of being turned on and off frequently without ruining the OS?

yes. You need the filesystem mounted readonly, then you can
flick the switch when you like.
There are various ways of doing this, but you'll need
some sort of ramdisk for a working filesystem while
the system is running.

> Question 2: Is the embedded version of Linux designed for a PC?  Or does the
> device have to be some weird, proprietary type?

There is no specific embedded type. Usually for embedded stuff you
need full control and so need to make your own version of linux kernel +
other support software. Linux (embedded or not) can run on various
platforms including the "PC". You may be able to get ideas from or use
some of the small/source distros listed at:
http://www.distrowatch.com/source.php
http://www.linuxhq.com/dist.html

> Question 3: Is there a way to boot Linux QUICKLY and load the software
> necessary immediately?

2 issues. The BIOS speed and the OS boot speed.
Standard PC BIOS' take about 15 second to boot,
which may be prohibitive. If so then you need to
look at:

http://www.gensw.com/pages/news/quikboot.htm
Note it has Embedded DOS rather than embedded Linux,
but who cares it's a BIOS. Full source code is provided.
Support for control of BIOS over serial port. You can also
download the binaries for free! The main advantage
is it boot's in 0.8s.

Other alternative BIOS' are
LinuxBIOS (3s)	http://freebios.sourceforge.net/
MrBIOS http://www.mrbios.com/

The second issue is the boot speed of linux
itself. With a modern CPU the kernel will
boot in about 1.5s on average, but then
you get to the initscripts which can and usually
take much longer. People working on helping
with this (parallelising init scripts basically) are:

Transmeta (midori)
Rusty Russell (Explicit initcall dependencies)


> 
> Thanks very much for your help.

Have a look at www.linuxdevices.com which should
have useful info and possibly more appropriate mailing lists ;-)

Padraig.