linux-kernel - Re: Please add generic support for root=UUID= at kernel parameter command line (LABEL, BYID maybe also)

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Message-ID: <20100823220506.7248c51b@schatten.dmk.lab>
Date:	Mon, 23 Aug 2010 22:05:06 +0200
From:	Florian Mickler <florian@...kler.org>
To:	linux-kernel@...r.kernel.org
Subject: Re: Please add generic support for root=UUID= at kernel parameter
 command line (LABEL, BYID maybe also)

On Mon, 23 Aug 2010 16:10:13 +0200
Eric Valette <Eric.Valette@...e.fr> wrote:

> Hi,
> 
> I just bought an new external disk enclosure with e-sata/USB2 connector 
> to replace an old USB2 only external disk enclosure.
> 
> My internal drive is a small SSD because I use the small factor PC as a 
> home theater and do want silence and fast boot. I build my own kernel to 
> put only what I need in and also boot somehow faster.
> 
> I use grub2 (up to date) as a loader. As soon as I power on the external 
> sata disk, the system does not boot because hardware designer add the 
> great idea to put the internal sata connector on ata3 whereas the 
> external e-sata is wired on ata2.
> 
> consequence is that root file system is on sda1 when no external drive 
> is connected and sdb1 when the external drive is connected.
> 
> As my grub setup was having a root=/dev/sda1 command line parameter and 
> it was advertised everywhere that root=UUID=xxxxx was now supported, I 
> changed the line to discover that this only work if an initramfs was 
> loaded because support is done entirely in used space! Reading 
> init/do_mounts.c made it very clear.
> 
> I find it extremely curious to have to add an initramfs to support 
> dynamic drive identification, especially when the BYID value is 
> displayed during boot message.
> 
> The boot loader cannot do a better job than the kernel and its life may 
> be even worse as bios value for the same disk may change according to 
> boot disk priorities.
> 
> Any hint comment? Any other way to avoid using a ramdisk? Please CC me 
> as I'm not subscribed.
> 
> -- eric
> 
> 
> 


I'm not exactly shure, but isn't the search command in grub2 what you
want?

http://forums.linuxmint.com/viewtopic.php?f=46&t=38599

You can let grub2 figure out which drive is which and pass the right
devices to the kernel...



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