Subject: kernel and root on different filesystems?
To: None <port-sparc64@netbsd.org>
From: Gert Doering <gert@greenie.muc.de>
List: port-sparc64
Date: 07/29/2007 11:57:10
Hi,

I'm not sure whether this is really "sparc64" specific, but then, booting
stuff usually *is* highly platform specific...

I run NetBSD on an Ultra5, which is handicapped by its very slow IDE
controller.  So I had the idea to put a faster IDE controller into the
machine, move all disks to the new controller, and use a CompactFlash
disk for booting the kernel from the onboard IDE.

The "easy" way would be to have / on the CompactFlash, and just mount
/usr etc. from the other IDE disks - but smaller (=cheaper) CF disks
have issues when overwriting the same sector too often, so one would
need to play "noatime" etc tricks.

What I can't seem to figure out is how to tell the system:

 - boot from "wd0a"  (= "boot disk" in OpenBoot)
 - mount root file system from "wd1a", load /sbin/init from there, etc.

I've read all man pages that show up on "man -k boot", but what I'm looking
for isn't there.

OK, well, there is a way - set the kernel option

    config          netbsd  root on wd1a type ffs

- but that's a compile-time thing, and means "this kernel won't be 
useful on anything with a different disk setup"...


On Linux, I'd just pass "root=/dev/hdb1" on the boot command line (and
put this into lilo.conf/grub.conf), but I can't find a document describing
whether I can do this with NetBSD as well, and if yes, what would be
the valid options.

Is this just something not possible, or am I overlooking "the" man page?

thanks,

gert

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Gert Doering - Munich, Germany                             gert@greenie.muc.de
fax: +49-89-35655025                        gert@net.informatik.tu-muenchen.de