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From: "H. Peter Anvin" <hpa@transmeta.com>
To: David Woodhouse <dwmw2@infradead.org>
Cc: linux-kernel@vger.kernel.org
Subject: Re: / on ramfs, possible?
Date: Mon, 30 Oct 2000 15:37:01 -0800	[thread overview]
Message-ID: <39FE061D.A68170B1@transmeta.com> (raw)
In-Reply-To: <Pine.LNX.4.21.0010302329140.16675-100000@imladris.demon.co.uk>

David Woodhouse wrote:
> 
> On Mon, 30 Oct 2000, H. Peter Anvin wrote:
> 
> > Pardon?!  This doesn't make any sense...
> >
> > The question was: how do switch from the initrd to using the ramfs as /?
> > Using pivot_root should do it (after the pivot, you can of course nuke
> > the initrd ramdisk.)
> 
> My question is: What do you want to do that for? You can nuke the initrd
> ramdisk, but you can't drop the rd.c code, or ll_rw_blk.c code, etc. So
> why not just keep your root filesystem in the initrd where it started off?
> 

Umm... because the size of a ramdisk is fixed, but the size of a ramfs is
flexible?

I can certainly understand this problem... I might in fact do exactly
this in the next version of my SuperRescue disk.  There, the ramdisk
which is the real root is populated from a .tar.gz file; the initrd is
just there to unpack the .tar.gz file onto the "real" ramdisk; the initrd
is then jettisoned.

Why not just have the real root be the initrd, you ask?  It's too large:
since an initrd needs to exist in both compressed form and uncompressed
form in memory at the same time; it would mean SuperRescue would no
longer work on systems with 64 MB RAM.  If I went to ramfs it might
actually work on systems with 48 MB RAM, albeit you better not need to
much space in / (or conversely, it would suddenly let you put a whole lot
more stuff in /tmp if you have 512 MB.)

	-hpa

-- 
<hpa@transmeta.com> at work, <hpa@zytor.com> in private!
"Unix gives you enough rope to shoot yourself in the foot."
http://www.zytor.com/~hpa/puzzle.txt
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  reply	other threads:[~2000-10-30 23:37 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2000-10-30  7:27 / on ramfs, possible? Anders Eriksson
2000-10-30  7:34 ` H. Peter Anvin
2000-10-30 23:24   ` David Woodhouse
2000-10-30 23:26     ` H. Peter Anvin
2000-10-30 23:32       ` David Woodhouse
2000-10-30 23:37         ` H. Peter Anvin [this message]
2000-10-30 23:39         ` Jeff Garzik
2000-11-01  9:16         ` aer-list
2000-10-30 12:42 ` Alan Cox
2000-10-30 20:09 ` Stuart Lynne
2000-10-30  8:39 Adam J. Richter

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