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Re: Ramdisk image on flash.

To: tpolgar@freehandsystems.com
Subject: Re: Ramdisk image on flash.
From: Mark Salter <msalter@redhat.com>
Date: Thu, 20 Feb 2003 15:16:22 -0500 (EST)
Cc: krishnakumar@naturesoft.net, linux-mips@linux-mips.org
In-reply-to: <3E55342D.6E1D36FF@freehandsystems.com> (message from Tibor Polgar on Thu, 20 Feb 2003 12:01:49 -0800)
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <200302201135.09154.krishnakumar@naturesoft.net> <1045765647.30379.262.camel@zeus.mvista.com> <3E552CDF.ECD08EEF@freehandsystems.com> <20030220194115.2A21378A6D@deneb.localdomain> <3E55342D.6E1D36FF@freehandsystems.com>
Sender: linux-mips-bounce@linux-mips.org
>>>>> Tibor Polgar writes:

>> >> On Wed, 2003-02-19 at 22:05, Krishnakumar. R wrote:
>> >> > Hi,
>> >> >
>> >> > Is there any way that I can keep
>> >> > a ramdisk image (containing the root filesystem)
>> >> > in a flash device and boot to it.
>> >>
>> >> Yes, and other architectures have support for passing arguments to the
>> >> kernel that tell it where the ramdisk is. I don't know that we've done
>> >> that for MIPS, yet.  It wouldn't be too hard to do and maybe someone on
>> >> this list is already working on it (I think someone actually is working
>> >> on it and was preparing a patch for Ralf).
>> 
>> > For having separate initrd and kernel load we also need an aware bootloader
>> > that knows where to find the ramdisk.   RedBoot, from what i read, seems 
>> > to be
>> > i386 specific.
>> 
>> Not at all. RedBoot can be used to pass a command line to MIPS kernels. It
>> would be simple to add the passing of a ramdisk address. It already supports
>> ramdisks from ARM and SH kernels.

> The original poster wanted a setup where the initrd was NOT part of the
> kernel, which begs the question of how/where it would be put into flash so
> something could load/uncompress it.   I'd love to have a way to decouple the
> two so i wouldn't have to recompile the kernel when i change the root image,
> but still not waste any space in flash.   I guess they could be written one
> after the other and the loader is just given a "load map" of where each one
> resides.   Would this satisfy Krishnakumar's requirements?

The ARM kernel separates the two and RedBoot handles that. There are a
number of approaches. Typically, RedBoot is used to store the separate
images in flash. You can then have a script that loads them into memory
and starts the kernel. You could have a script grab the two images off
of a tftp server. etc.

--Mark



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