[ale] SW RAID install problem - can't find root on raid at boot time

[Danny Cox]

> > On Tue, 2006-08-29 at 09:46 -0400, Jeff Hubbs wrote:
> >   
> >> Having all manner of trouble with this.
> >>
> >> Two SATA drives; onboard RAID disabled in favor of SW RAID:
> >>
> >>   ptn |   1   |   2   |   3   |
> >>  disk ------------------------
> >>   sda | /boot |  md1  |  md2  |
> >>   sdb | spare |  md1  |  md2  |
> >>
> >> The goal here is to mount /dev/md1 at boot.
> >>
> >> At boot, I get:
> >>
> >>   md: autodetecting raid arrays
> >>   md: autorun...
> >>   md: ...autorun done
> >>   VFS: cannot open root device "md1" or unknown-device(0,0)
> >>   please append a correct "root=" boot option
> >>   Kernel panic - not syncing: vfs : unable to mount root fs on
> >> unknown-block(0,0)

	Well, the auto-detect isn't working.  When it works correctly, you'll
see something like this:

md: Autodetecting RAID arrays.
md: autorun ...
md: considering hde1 ...
md:  adding hde1 ...
md:  adding hdb2 ...
md: created md0
md: bind<hdb2>
md: bind<hde1>
md: running: <hde1><hdb2>
md: raid1 personality registered for level 1
raid1: raid set md0 active with 2 out of 2 mirrors
md: ... autorun DONE.

	I think the problem is that root is mounted first, and then LATER, RAID
autodetect is invoked.  So, /dev/md1 isn't available yet.  There's a
trick to this.  At one time you mounted one disk of the array just to
get things going, and later, when the array was activated, a
"switchroot" was done to establish the root fs on the RAID.

	See http://tldp.org/HOWTO/Software-RAID-HOWTO-7.html#ss7.3 for specific
information on setting up GRUB to use it.  Sorry, I don't remember if
you said you're using GRUB or not.  Hope this helps!

-- 
Daniel S. Cox
Internet Commerce Corporation