[uml-user] VFS: Cannot open root device "root_fs" or unknown-block(0,0)

[Zack G. <zac...@gm...>]

Hi Everybody,

I'm try to get UML up and running, but I can't get it to recognize my
root filesystem.  Here's a little background on my process thus far.

I'm running Debian.

I built UML from source, using the 2.6.11.5 linux kernel.

I didn't apply the patch because this version is new enough to have
UML support built in as part of the kernel.

At first I didn't change any of the kernel config options, but after
trolling through the list archives for a while I found someone who
solved this problem by enabling BLK_DEV_UBD and BLK_DEV_UBD_SYNC, so I
tried that too (it didn't help).

I've tried three different pre-built filesystem so far:
Debian-3.0r2.ext2, Debian-3.0r2.ext2, and root_fs_toms1.7.205.

I've played around with passing the command line option devfs=nomount.

I created the file dev/ubd/disc0/disc on the guest filesystem, using
the method found here:
http://sourceforge.net/mailarchive/forum.php?thread_id=6773617&forum_id=3647 
<http://sourceforge.net/mailarchive/forum.php?thread_id=6773617&forum_id=3647>
Despite that, when I attempt to run colinux, it says dev/ubd/disc0:
unknown partition table right before the error message in the subject
line.

Another interesting thing I've noticed: if I pass a command line
argument cobd0= instead of root=, the error message if VFS: Cannot
open root device (0:98) instead of displaying the name of the
filesystem.

So, anyone have any idea what I'm doing wrong?  I can't really think
of anything else to try at this point.
-Zack Galbreath