Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 14 Mar 2003 15:39:47 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 14 Mar 2003 15:39:47 -0500 Received: from neon-gw-l3.transmeta.com ([63.209.4.196]:57094 "EHLO neon-gw.transmeta.com") by vger.kernel.org with ESMTP id ; Fri, 14 Mar 2003 15:39:40 -0500 Message-ID: <3E723ECD.8010000@zytor.com> Date: Fri, 14 Mar 2003 12:42:53 -0800 From: "H. Peter Anvin" Organization: Zytor Communications User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.3b) Gecko/20030211 X-Accept-Language: en, sv MIME-Version: 1.0 To: Chris Friesen CC: linux-kernel@vger.kernel.org, kai@tp1.ruhr-uni-bochum.de Subject: Re: Kernel setup() and initrd problems References:

<3E722D31.6050702@nortelnetworks.com> <3E7230D2.7010309@zytor.com> <3E7235B7.5050407@nortelnetworks.com> In-Reply-To: <3E7235B7.5050407@nortelnetworks.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1889 Lines: 53 Chris Friesen wrote: > H. Peter Anvin wrote: > >> Chris Friesen wrote: >> >>> >>> Below is the script that I used to pivot from a standard ramdisk (for >>> with >>> the infrastructure is already in place in our build environment) to a >>> tmpfs >>> filesystem. This requires no changes to the boot args. > > >> ... which means that you either have boot args or rdev so that >> /dev/ram0 is the root filesystem (or it wouldn't work.) > > > Yes, but after the pivot, /dev/ram0 isn't the real filesytem, its tmpfs > mounted at /. Isn't that what the original poster was talking about, > where the root on the final running system is not the same as what the > machine was booted with? > > Maybe I'm just confused. > I think so. The fundamental problem is that the original initrd protocol considered the initrd to be something different than "a real root", and its init (linuxrc) to be something different than "a real init." With pivot_root, all of that is historical baggage, and worse - it gets in the way. The way to get around the historical baggage is to tell the kernel that the initrd is a "permanent" initrd by using the "root=/dev/ram0" command-line option. This has the side effect of bypassing all the initrd historical crap and instead spawning /sbin/init using PID 1, like any other system would do. Now you can just pivot and "exec /sbin/init" like you should be. Of course, after the pivot_root, the root is something completely different than the root= command-line option states, but that's irrelevant. The command-line option is there to disable the initrd historical garbage, not for any other purpose. -hpa - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/