linux-kernel - Re: Initramfs from existing vmlinuz

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Message-ID: <20090105114730.GD3268@1wt.eu>
Date:	Mon, 5 Jan 2009 12:47:30 +0100
From:	Willy Tarreau <w@....eu>
To:	Ian Campbell <ijc@...lion.org.uk>
Cc:	Martin Schlemmer <Martin.Schlemmer@....ac.za>,
	linux-kernel@...r.kernel.org
Subject: Re: Initramfs from existing vmlinuz

On Mon, Jan 05, 2009 at 11:12:26AM +0000, Ian Campbell wrote:
> On Wed, 2008-12-24 at 00:34 +0100, Willy Tarreau wrote:
> > You first have to extract and uncompress the ELF image from vmlinuz.
> > For this, look for the gzip signature 1F 8B 08 in your vmlinuz, and
> > feed all data starting from this point to zcat.
> 
> Since v2.6.26 (I think, it was v2.08 of the x86 bzImage format anyhow,
> which was the same point the payload became ELF formatted) you can find
> it directly using the payload_offset and payload_length fields in the
> bzImage header. Attached bzexplode.c demonstrates this. e.g. "bzexplode
> vmlinuz | zcat > vmlinux.elf"

Thanks Ian.

Indeed, I'm sure this will be useful from time to time!

Cheers,
Willy

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