PC104 board boot off compact flash, load initrd, and execute out of ramdisk

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Need some help here if anyone can spare a minute.

I have been working (ok struggling) with this project for some time.
It is a PC/104 industrial board running Linux.  The board is basically
a normal computer (AMD Geode 300mhz x86 processor, SODIMM memory, 2 IDE
channels, usb, ethernet, etc), all normal stuff.  Currently I have a
hard-drive and CDROM connected to one IDE channel and the other IDE
channel is dedicated to a on-board compact-flash socket.  With this
setup I installed Gentoo Linux onto the hard-drive, got it all working
fine and honestly it's pretty slick for a 3.5"x3.5" computer.

Now, I need to get this to the customer, which means the hard-drive and
CDROM go away, it needs to boot entirely off the compact-flash card,
load a initial ramdisk (initrd) and execute out of that.

I have read everything I can find about this and it certainly appears
do-able.  I created my initrd image file using the 'dd' command then
'mount -o loop...' etc, I stripped down alot of stuff from my actual
system here since I'm using about 1.8gig on the hard-drive, but
compact-flash card is only 512meg, and more importantly RAM is only
256meg on this board (although that could be upped easily if needed).
The CF card shows up as /dev/hdc according to Linux, I can read/write
to it happily, it appears Linux doesn't know or care it's a CF card
(the BIOS shows it as a hard-drive also).

So I have it starting to boot, have the CF card formatted, a kernel on
it (2.6.9 that I compiled).  I am using syslinux as the boot loader and
it starts up, finds the image file (lite.gz) and says it finds the
kernel, and starts uncompressing the kernel.  Works for 10-15 seconds,
then halts with a "Kernel Panic - Not Syncing: VFS: Unable to mount
root fs on unknown (0,0)".  I looked that error up and usually it's
because of a "root=" or "boot=" directive wrong in the boot loader, so
it's not passing the correct info to the kernel.
Soooo, I'm trying to learn what is a 'correct' way to pass argument to
the kernel, I have grub and lilo both I can use (grub seems to have
issues though, I just compiled lilo because most examples I've seen use
it, I know any should work, but monkey see, monkey do, I'm happy to
copy a working system).

I would greatly appreciate it if someone could post what either their
grub.conf, or lilo.conf, or syslinux.cfg files are to load a initrd at
startup, then change-root, or switch-root or whatever it's called where
you make the root file-system the ramdisk you just created.  I read
that I need a /linuxrc file which will be executed immediately after
the initrd is created/expanded, I'm alittle lost with that however.  I
have read many versions of /etc/fstab files, some using /dev/ram0, some
/dev/ram1, some /dev/rd/0/, some /dev/mem...a ton of variations, I just
am looking for what will load a initrd then run out of it, with no
hard-drive or cdrom or anything around.

I found one other writeup which has helped some (not enough or I
wouldn't be here), in that example the initrd was mounted as the root
drive, but then the CF card was remounted as /etc or something like
that, so in the running program you could write out to real storage
(writing to the initrd does no good for keeping anything ofcourse), and
you could specify a program to run at startup which wouldn't have to be
in that image, so you could say always run /etc/MyProgram, so then to
update your program, you'd just over-write that file on the flash-card
with a new version, never touching the actual file system image.

The compact-flash card ideally needs to stay as a FAT16 card, as we
have plans of using Windows computers with USB CF readers to load these
in the field.

So that is the plan, any help is greatly appreciated.  I'm not a linux
guru, never worked much with this at all, know almost nothing, yet I am
the most knowledable person (linux-wise) working on this
project...eeeek...

Thanks in advance!
Mark Brodis


Re: PC104 board boot off compact flash, load initrd, and execute out of ramdisk

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Read about the "rdev" tool to plug in the root device information
directly; no kernel command line needed.


Re: PC104 board boot off compact flash, load initrd, and execute out of ramdisk
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...

If your PC-104 board can boot off USB device, then you might be
interested in
    http://home.eol.ca/~parkw/thinflash.html

It's designed as Linux thin-client, but you can use it in any way you
want.  At the momemt, it's 256MB with no room to spare.  So, if you use
1GB USB key, then you have 750MB leftover.

By the way,
    - what brand of PC-104 are you using?
    - how much does it cost?
    - any URL?

--
ThinFlash: Linux thin-client on USB key (flash) drive
We've slightly trimmed the long signature. Click to see the full one.
Re: PC104 board boot off compact flash, load initrd, and execute out of ramdisk
I think it can boot off a USB device although we are not using any USB
stuff and therefore did not purchase the little pigtails that would go
onto this board.

The board is made by Kontron, it was in the neighborhood of $300 with
256meg of SO-DIMM (std laptop memory) installed in the one memory slot,
I didn't decide on this model, but this is what was purchased.

Here is the URL to the board:
http://www.kontron.com/products/pdproductdetail.cfm?keyProduct31%751&kps10%40&kpc13%5

It's a cute little board, and pretty powerful, basically a full desktop
system, minus the drives in a 3.5"x3.5" computer, also no fan is needed
for the CPU and the whole board runs off 5v.

With the help of some major linux gurus I have almost gotten this thing
to reliably boot, it is very odd how it works and extremely
frustrating, a big problem has been with bootloaders.  They seem
inheriently flawed to me, when I'm in a running system (off the HD) the
CF card shows up as /dev/hdc, however with a newer kernel a buddy gave
me it *should* showup as /dev/discs/disc0/disc, but it doesn't, well it
kinda does, to get it to boot you HAVE to pass "root=/dev/hdc1 rw" to
the kernel, even on the newer kernel that when fully booted does not
have /dev/hdc in it's /dev directory, then it apparently sees the
partiion as /dev/discs/disc0/part1 which is should...it is very odd and
there is something fishy going on between the bios and the bootloader
and kernel...it's been a total mess to be honest with you and I would
never do this again without some more help.  Every writeup I have found
that gave nice clear instructions on how to do this would not work,
simple as that, enter this command, the root drive should be here,
etc...didn't happen that way.  Cute board but not a fun project...


Re: PC104 board boot off compact flash, load initrd, and execute out of ramdisk
/dev/hdc as a kernel argument is for pointing the kernel to the correct
driver; your filesystem image itself must contain the necessary block
special file to point to the correct driver...

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http://www.kontron.com/products/pdproductdetail.cfm?keyProduct31%751&kps10%40&kpc13%5
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