Boot linux from cramfs on USB

[Sascha Hauer]

On Mon, Apr 02, 2012 at 05:33:11PM +0200, Jakob Malm wrote:
> Hi,
> 
> Thanks for your prompt reply!
> 
> Den 2 april 2012 16:29 skrev Sascha Hauer <s.hauer at pengutronix.de>:
> > That said, your setup seems a bit crazy. What is inside your cramfs? The
> > kernel? You should rather put your kernel into a plain partition on the
> > USB disk. Or do you only have your rootfs inside the cramfs? I rather
> > recommend ext2 or ext3 for this.
> 
> The cramfs would contain the rootfs, including kernel.
> 
> I want to be able to have FAT on the disk, preferably with a single
> file (possibly two), containing the kernel and rootfs, and then load
> up the rootfs into memory and start the kernel with that rootfs. I
> suppose I could create a command specific for our case, but it seems
> like a common enough scenario to me that someone else should have done
> something similar...

You can extract the kernel from your cramfs image by fixing the cramfs
support. I just saw that cramfs expects a /dev/ file, that is it expects
a devfs file. This could be changed by using regular open/read/write
functions.
It would be easier though if you live with two files, one cramfs image
and one kernel image.

Sascha

-- 
Pengutronix e.K.                           |                             |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |