Message-ID: <4F395AFE.9010802@zytor.com>
Date: Mon, 13 Feb 2012 10:48:30 -0800
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Kirill Smelkov <kirr@mns.spb.ru>
CC: Paul Parsons <lost.distance@yahoo.com>, Kay Sievers <kay.sievers@vrfy.org>,
        linux-kernel@vger.kernel.org
Subject: Re: No /dev/root with devtmpfs?
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On 02/13/2012 12:25 AM, Kirill Smelkov wrote:
>>
>> The bootloader might pass the root partition to the kernel via the
>> "root=" kernel parameter; these can be read at /proc/cmdline.
>> For example, on an HP iPAQ hx4700: root=/dev/mtdblock2
> 
> This does not work universally either, for example for
> 
>     root=PARTUUID=00112233-4455-6677-8899-AABBCCDDEEFF
> 
> 
> the kernel scans partitions and finds one for root by partition uuid
> (see name_to_dev_t() in init/do_mounts.c).
> 
> That's exactly my situation - I have universal flash image which can
> bee booted via CF slot (on several boards, thus will have different
> /dev/hd? or /dev/sd?) and via usb/cardreader (again different /dev/
> entry), and root is mounted by partition id.
> 
> The kernel has no problem finding root partition and mounting it. I just
> needed a sane and robust way to know its choice.
> 

In this case it's not the kernel, but the initramfs which does this
lookup.  In that case the initramfs could/should create /dev/root.

	-hpa

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

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