linux-kernel - Re: [RFC][PATCH] init: Open /dev/console from rootfs

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Date:	Wed, 03 Mar 2010 00:35:00 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	linux-kernel@...r.kernel.org, Al Viro <viro@...IV.linux.org.uk>,
	Kay Sievers <kay.sievers@...y.org>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: Re: [RFC][PATCH] init: Open /dev/console from rootfs

On 03/02/2010 11:53 PM, Eric W. Biederman wrote:
> 
> To avoid potential problems with an empty /dev open /dev/console
> from rootfs instead of waiting to mount our root filesystem and
> mounting it there.   This effectively guarantees that there will
> be a device node, and it won't be on a filesystem that we will
> ever unmount, so there are no issues with leaving /dev/console
> open and pinning the filesystem.
> 
> This is actually more effective than automatically mounting
> devtmpfs on /dev because it removes removes the occasionally
> problematic assumption that /dev/console exists from the boot
> code.
> 
> With this patch I was able to throw busybox on my /boot partition
> (which has no /dev directory) and boot into userspace without
> problems.
> 
> The only possible negative consequence I can think of is that
> someone out there deliberately used did not use a character device
> that is major 5 minor 2 for /dev/console.  Does anyone know of a
> situation in which that could make sense?
> 

There probably are ... but if so, they can just re-open their new
console of choice after creating it, and/or use an initramfs which
overrides the default /dev/console.

As such, this makes a lot of sense to me.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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