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Date:      Wed, 1 Sep 1999 18:46:57 +0300
From:      Ruslan Ermilov <ru@ucb.crimea.ua>
To:        David Kelly <dkelly@HiWAAY.net>
Cc:        freebsd-stable@FreeBSD.org
Subject:   Re: wiring down SCSI devices, and the root device
Message-ID:  <19990901184657.A77510@relay.ucb.crimea.ua>
In-Reply-To: <199909010317.WAA00426@nospam.hiwaay.net>; from David Kelly on Tue, Aug 31, 1999 at 10:17:33PM -0500
References:  <199909010317.WAA00426@nospam.hiwaay.net>

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On Tue, Aug 31, 1999 at 10:17:33PM -0500, David Kelly wrote:
> Messing around with SCSI drives and two SCSI controllers. One is a 
> first generation Adaptec 2940A, fast, narrow. The other is a much newer 
> Sybios 875-based card. Apparently I have them in the wrong PCI slots to 
> boot the way I wish if a HD is on the Adaptec. "Normally" only tape 
> drives are on the Adaptec. And only one HD is on ncr0.
> 
> So rather than solve my problem in hardware, thought I'd do it in
> software. Altered my config file to wire down my SCSI devices like this
> (thought I'd throw in the "kernel root on" for completness):
> 
> config          kernel  root on da0
> 
> # old way:
> #controller     scbus0
> #device         da0
> #
> # wired down:
> controller      scbus0  at ncr0
> controller      scbus1  at ahc0
> device          da0     at scbus0 target 0
> 
> The comments in LINT suggest "device" and "disk" are the same thing so 
> I commented out the old "device da0" and used the LINT disk line as my 
> example.
> 
> Is the "controller scbus1" line needed? Based on the LINT example I 
> didn't think it could hurt.
> 
> Built and installed new kernel. Shut down. Added a 2G HD to the ahc0. 
> During boot BIOS says this new HD is the C: drive. Fromerly the 9G 
> drive on ncr0 was so identified.
> 
> My boot block code says something about version 0.7.
> 
> F5 to boot second disk. Then the normal F2 to boot BSD. Eventually 
> followed by a fatal error. This part is typed from written notes:
> 
> da1 at ahc0 bus 0 target 1 lun 0
> ... (normal da1 stuff for the new HD)
> changing root device to da1s1a
> error 22: panic: cannot mount root(2)
> (2 blank lines)
> syncing disks... done
> da0 at ncr0 bus 0 target 0 lun 0
> ... (normal da0 stuff for the old HD)
> Automatic reboot in 15 seconds - press a key on the console to abort
> 
> For some reason my kernel reassigned root contrary to my instructions 
> in config. And after deciding to sync and reboot apparently a process 
> or thread or something completed the probe of da0, which was supposed 
> to be root. And finally the shutdown completed.
> 
> System is 3.2-STABLE, cvsup'ed the evening of 8/30/99. Matching kernel. 
> But using my config. I don't see anything in GENERIC addressing 
> possible solutions.
>
Normally, the system uses the device from which it was booted as the root
device if possible.  (See reboot(2) and boot(8) for details).

There are a lot of possible solutions:

1) Hit any key while the boot blocks are loading (thus skipping an invokation
   of the third-stage loader(8)), and type `-r' to boot blocks prompt.
   Refer to the boot(8) manpage.

2) Inside loader(8), interrupt the autoboot sequence by pressing <Space>
   and type `boot -r' on the command prompt.
   Refer to the loader(8) manpage.

3) Inside loader(8), set `rootdev' variable to the appropriate value
   and execute `boot'.  Or better yet put this into /boot/loader.conf.
   Refer to the loader(8) and loader.conf(8) manpages.


Cheers,
-- 
Ruslan Ermilov		Sysadmin and DBA of the
ru@ucb.crimea.ua	United Commercial Bank,
ru@FreeBSD.org		FreeBSD committer,
+380.652.247.647	Simferopol, Ukraine

http://www.FreeBSD.org	The Power To Serve
http://www.oracle.com	Enabling The Information Age


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