Setting up compressed rootfs on DOC

Setting up compressed rootfs on DOC

[Selwyn Tang]

Hi all,

I am used to running a DOC patched grub firmware on my DOC 2000 (16MB)
with nftl, following the instructions of Karim's book. Since the space
is running out, I am interested in using a compressed root fs.

I followed mtd-jffs-HOWTO.txt (1.16) to build a compressed root fs on
DOC. That is, I copied my root fs to a ramdisk, dd'd it through gzip to
a compressed gz file, dd'd it to an offset of 1MB on /dev/mtd0 and
rdev'd the kernel image (967KB) about the offset and the device to be
used. Then I came to a problem of how to install the kernel on the DOC.

The HOWTO says I can use any boot loader, like lilo, to install the
kernel, or just place the kernel on the device and boot from it
directly. I got confused here, as I am used to using a grub firmware,
which hooks to int 19h as a bios extension. When it is booted, it
understands the DOC and can load my kernel image from my root fs on the
ext2 partition on the DOC.

But in here, how should I install my kernel image? I tried dd'ing it to
the start of my DOC, like creating a boot floppy, but it doesn't seem
like a boot device to the bios. Should I still install a grub firmware
and a small partition for storing my kernel image, and then dd my
compressed root fs after the partition? Or is there any other more
clever ways?

Selwyn

Re: Setting up compressed rootfs on DOC

[Selwyn Tang]

Dear Russ,

Thanks for your response. I thought no one was interested in my question.

On 11/16/2003 01:18 AM, Russ Dill wrote:
> On Fri, 2003-10-24 at 02:16, Selwyn Tang wrote:
> 
>>Hi all,
>>
>>I am used to running a DOC patched grub firmware on my DOC 2000 (16MB)
>>with nftl, following the instructions of Karim's book. Since the space
>>is running out, I am interested in using a compressed root fs.
>>
>>I followed mtd-jffs-HOWTO.txt (1.16) to build a compressed root fs on
>>DOC. That is, I copied my root fs to a ramdisk, dd'd it through gzip to
>>a compressed gz file, dd'd it to an offset of 1MB on /dev/mtd0 and
>>rdev'd the kernel image (967KB) about the offset and the device to be
>>used. Then I came to a problem of how to install the kernel on the DOC.
>>
>>The HOWTO says I can use any boot loader, like lilo, to install the
>>kernel, or just place the kernel on the device and boot from it
>>directly. I got confused here, as I am used to using a grub firmware,
>>which hooks to int 19h as a bios extension. When it is booted, it
>>understands the DOC and can load my kernel image from my root fs on the
>>ext2 partition on the DOC.
>>
>>But in here, how should I install my kernel image? I tried dd'ing it to
>>the start of my DOC, like creating a boot floppy, but it doesn't seem
>>like a boot device to the bios. Should I still install a grub firmware
>>and a small partition for storing my kernel image, and then dd my
>>compressed root fs after the partition? Or is there any other more
>>clever ways?
> 
> 
> you can't put files on raw nand flash like you can on nor flash. You
> need some sort of filesystem, and grub needs to understand that file
> system. The only compressed filesystem I know of that grub can read, is
> cramfs.
> 

Do you mean I still have to use a DOC patched Grub firmware, and dd my
root fs, prepared as a cramfs image, to my DOC? I really have no idea of
what I have to do exactly. Can you offer me some more details?

Selwyn

Re: Setting up compressed rootfs on DOC

[David Woodhouse]

On Fri, 2003-10-24 at 17:16 +0800, Selwyn Tang wrote:
> Hi all,
> 
> I am used to running a DOC patched grub firmware on my DOC 2000 (16MB)
> with nftl, following the instructions of Karim's book. Since the space
> is running out, I am interested in using a compressed root fs.

There is no clever way to do this out of the box. If I needed this, I'd
do it as follows:

1. Fix the new NAND/DiskOnChip driver so it does hardware ECC and 
   correctly reads and enforces the Bad Block Table.

2. Use JFFS2 on your DiskOnChip.

3. Find/make a bootloader which can live in the DiskOnChip where
   Grub currently is and which groks JFFS2 so it can find and boot
   kernels from the file system. I'd probably use RedBoot for this,
   since the JFFS2 code is designed to work in eCos (on which
   RedBoot is based) and hence it shouldn't be hard to make
   JFFS2/NAND work in RedBoot.

You could skip step 3 if you put a tiny NFTL partition at the beginning
of the flash to hold the kernel, and just use JFFS2 on the rest.

-- 
dwmw2