Thanks for all the replies. After reading all the
helpful response. I think I will try to use initrd,
and probably try ramdisk, too. I don't necessary need
to run with a minimum system. The hardware has 8M,
and I will try 1M for ramdisk. It seems like this
is the easiest way to get thing starts.

--- Jerry Van Baren <vanbaren_gerald@si.com> wrote:

You need at least a RAM file system for "/" and a
bunch of subdirectories
such as /dev, /lib, etc.  The common way to do this
on a minimalistic
system is to create a file system image in ROM
(often compressed) and copy
it to RAM on start up.  Given the questions you are
asking, I am very
confident creating a minimal RAM disk image will
challenge you sufficiently
:-).  I'm not being snide, lots of people with lots
of linux knowledge have
tried and failed.  Most people use someone else's
pre-configured minimal
file systems and add/subtract (mostly add :-)
programs to it.  This is
because it is very, very hard to create a minimal
file system (that works,
that is).

Pointers to development systems with example RAM
disk images:
   http://www.denx.de/solutions-en.html
     ftp://ftp.denx.de/pub/LinuxPPC/usr/src/SELF/
   http://www.mvista.com/
   (there are others, I'm just too lazy to do the
google search for you)

Trying to run linux without a file system of any
sort would require you to
rewrite of pretty much everything and the three or
four things you didn't
rewrite, you would have to rebuild (static link, no
shared
libraries).  There are a lot of software engineers
and hackers that would
turn down the opportunity to do this at any price.
On the other hand, a
lot of naivety and a even more coffee sometimes
generates remarkable
results :-).

You really want to look at eCOS or one of the other
light weight tasking OSs.
   http://www.redhat.com/embedded/technologies/ecos/

gvb

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