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Date: Thu, 17 Mar 2005 15:59:14 +0100
From: Patrick Huesmann <patrick.huesmann@gmail.com>
To: "Robert P. J. Day" <rpjday@mindspring.com>
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Cc: linuxppc-embedded@ozlabs.org
Subject: Re: looking for a model for building CRAMFS(?)-based system
Reply-To: Patrick Huesmann <patrick.huesmann@gmail.com>
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Hi,

On Wed, 16 Mar 2005 11:33:39 -0500 (EST), Robert P. J. Day
<rpjday@mindspring.com> wrote:
>   currently, the system i've built for our 850 board incorporates
> 
>         - boot loader (sadly, not u-boot, but i'm working on it)
>         - standard zImage.initrd.bin kernel+initrd image
>         ... mountable JFFS2 filesystem with persistent stuff ...
> 
>   obviously, with this layout, it's kind of a nuisance to update
> anything individually in the initrd portion of the system, so i'd like
> to at least experiment with a layout that has separate
> 
>         - boot loader (ideally, u-boot)
>         - kernel image
>         - updateable (normally mounted read-only?) root filesystem
>         ... rest of stuff the same ...

I'm using separate MTD partitions for bootloader, device parameters,
zImage, initrd and persistent storage.

When updating the initrd, the only thing necessary is a
eraseall /dev/mtdX
cat initrd.gz > /dev/mtdX

When booting the kernel, you need something like this in the commandline:
root=/dev/mtdblockX prompt_ramdisk=0 load_ramdisk=1 ramdisk_size=8192

This is bootloader independent, of course.

HTH,
Patrick