JFFS2 as root FS

[Joakim Tjernlund]

----- Original Message -----
From: "Vipin Malik" <vipin.malik at daniel.com>
To: "Joakim Tjernlund" <Joakim.Tjernlund at lumentis.se>
Cc: <mtd at infradead.org>
Sent: den 18 april 2001 22:19
Subject: Re: JFFS2 as root FS


> Joakim Tjernlund wrote:
>
> > ----- Original Message -----
> > From: "Vipin Malik" <vipin.malik at daniel.com>
> > To: <joakim.tjernlund at lumentis.se>
> > Cc: <mtd at infradead.org>
> > Sent: den 18 april 2001 19:11
> > Subject: Re: JFFS2 as root FS
> >
> > > Joakim Tjernlund wrote:
> > >
> > > > Hi there
> > > >
> > > > Has anybody managed to get a root FS with JFFS2 to work?
> > >
> > > Sure! But as you say that you followed the HOWTO, and since I wrote
the
> > > HOWTO,
> > > I guess that something in my procedures tripped you up that worked ok
for
> > > me :)
> >
> > Dont think so, I think it's me :-)
> >
> > >
> > >
> > > >
> > > > I followed the mtd howto and I have a root partition(with the
necessary
> > > > files) and
> > > > all I get is: "Kernel panic: I have no root and I want to scream"
> > > > message.
> > >
> > > Hmm, what kernel version are you using? I've never seen that message
(I've
> > > seen Kernel panic: Unable to open root..blah blah..)
> >
> > I using a 2.4 kernel I pulled from Cort Dougan's PPC tree a few weeks
ago.
> > Can't remeber which version rigth now, I will have to check when I get
back
> > to work tomorrow. Should I change to the latest official kernel(2.4.3)?
>
> I don't know. Never played with a non-x86 kernel (well if you don't count
the
> dragonball kernel variant).
> I wouldn't think that you would need to update to the latest one, but i'll
let
> someone who know's reply.
>
> Make sure that you have the latest sources from CVS patched in though. You
> don't want to be playing with the
> default mtd/jffs stuff that came with the kernel.

yeah, I have the latest sources.

>
>
> >
> >
> > >
> > >
> > > >
> > > >
> > > > first I tried to use "rdev zvmlinux /dev/mtdblock1", but
> > > > the kernel ignored that an did a NFS mount as usual.
> > >
> > > Wait, wait, wait. What do you mean by this? This is *a problem* right
> > > here.
> > >
> > > Why is it doing a NFS mount? Please describe your config and what you
are
> > > trying to do.
> > > "usual" kernels don't NFS mount their root fs!
> >
> > I am using an RPX CLLF board with a PPC869T. I found a config under
> > arch/ppc/defconfigs
> > (If my memory don't fail me)
> >
> > In that config there were an automount(??) option enabled and a Root fs
on
> > NFS option also
> > enabled.  I will  disable them and se what happens.
>
> I don't think that just enabling these options actually *does* mount root
over
> nfs. It just allows
> it. (Disclaimer: I've never mounted root over nfs myself so take this with
a
> pinch of salt).

hmm, there has to be something in my config which takes precedence over
rdev, otherwise
the kernel would try to mount mtdblock1 instead of doing a NFS mount. The
kernel
does a BOOTP request to find its IP address, maybe that also implies to
mount a NFS root
instead of mtdblock1?

>
> >
> >
> > >
> > >
> > >
> > > > I then
> > > > specified on the kernel commad line: root=/dev/mtdblock1
> > > > and the I got the kernel panic above.
> > >
> > > Well, the kernel may not be able to understand the "mtdblock1" device
by
> > > name unless you patched
> > > the init/main.c file to list a conversion table from mtdblockxx to a
> > > *device number*.
> >
> > Well, this I have not done. Cant remember I saw that in the mtd howto,
is
> > that patch
> > included in later kernels?
>
> You don't need to apply the patch if you stick with the rdev stuff, as
that
> uses device numbers to
> tell the kernel what root is.

would be nice to try this patch to see if things start to work. Do how this
patch
looks?

>
> You may have to dive into the kernel sources and put prink's to see that
your
> kernel thinks root device is
> that it's  trying to mount. That'll tell you where the problem lies in the
> first place.
>
> If it doesn't say something like 31:1 (for /dev/mtdblock1) then your rdev
> command did not take. Investigate that then.
>
> If your root device is correct then investigate why it could not mount it.
You
> did run lilo after you did rdev?

Currently I let the RPX firmware boot the kernel via tftp. Is that whats
causing my problems?
I have not tried LILO since I think it can only handle x86. Can it do PPC as
well(with a JFFS2 root FS)?

>
>
>
> >
> >
> > Other questions i have:
> >
> >   Is mkfs.jffs2 Endian safe? I mean can I run mkfs.jffs2 on an Intel PC
and
> > then copy it to my RPX board?
>
> There *are* people using mtd/jffs on PPC. See the list archives for some
issues
> that people have had and their possible solutions.
>
> Hmm, you'r not trying to mount jffs as root before you can manually mount
it as
> a "regular" partition under full manual control?

No, I have mounted it manually first and then copied required files more or
less by hand.
I tried mkfs.jffs2, but it didn't work for me. Maybe I am doing something
wrong?
I did this: mkfs.jffs2 -d <path to my root fs dir> -o rootfs.image -e
0x40000
then on RPX: eraseall /dev/mtd1; cp rootfs.image /dev/mtd1(or was it
mtdblock1?)

that gave me lots of errors when mounting JFFS2 on /dev/mtdblock1
(don't have the error messages handy now)

Does mkfs.jffs2 handle dev files & sym links correctly?

> If you have endian issues, they should pop up at that time. Debugging
endian
> issues and root mounting problems is not a good plan.

heh, not a very good plan at all :-)

>
>
> >
> >
> >   Is there a way to disable compression in JFFS2?
>
> Not that I know of. I think it's in the to-do list. Ask David W.

David, is it possible?

>
> >
> >
> > I have also noted that sym links in JFFS2 have zero size,  a bug?
>
> David?
>
>
> Vipin

       Jocke



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