Re: USB stick as root device does not work

From: Micha Nelissen
Date: Mon May 23 2011 - 14:06:35 EST

Hi all,

Alan Stern wrote:
> On Mon, 23 May 2011, Randy Dunlap wrote:
> Better to ask people familiar with the block layer (CC'ed).

I found out what happened: I use LILO, and lilo was not passing
root=/dev/sdb1 on the commandline, but root=811. However, I didn't see
that since on i386 that part had already scrolled off-screen. I found
out by accident, due to a user space program trying to parse that,
expecting a string, getting a number :-).

Using the following in my lilo.conf:

append="root=/dev/sdb1 rootwait"
instead of

works perfectly. Maybe this information is useful for somebody else; I
did not find it using a quick google.

Thanks for your attention.


>> On Sun, 22 May 2011 16:13:17 +0200 Micha Nelissen wrote:
>>> Hi,
>>> Using USB stick as root device does not work for me. I specify
>>> 'root=/dev/sdb1 rootwait' on the kernel commandline, but the kernel does
>>> not wait for the USB stick to be scanned and its partitions found. I
>>> have a harddisk which is /dev/sda, and this USB stick would be /dev/sdb.
>>> I think blk_lookup_devt returns the block device number even if it does
>>> not exist yet, and init/do_mounts.c:473 therefore skips waiting:
>>> if ((ROOT_DEV == 0) && root_wait) {
>>> due to ROOT_DEV having become non-zero already.
>>> If I use the commandline: 'root=/dev/sdb1 rootdelay=5' then it does
>>> mount and boot properly. However, using rootwait seems safer and faster
>>> to me, that it's meant for this use case.
>>> Thanks for any pointers,
>>> Micha
>>> --
>> ---
>> ~Randy
>> *** Remember to use Documentation/SubmitChecklist when testing your code ***
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