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Date:      Fri, 22 Jan 2010 13:30:35 -0500
From:      Nathan Vidican <>
To:        Billy Newsom <>
Subject:   Re: How to troubleshoot a frozen boot sequence
Message-ID:  <>
In-Reply-To: <>
References:  <>

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To me, it sounds like you have two issues to deal with here:

#1 - booting off of the twed0 disk, what is your systems' BIOS currently set
to boot from, from the way you describe it's almost as if the system is
booting from ad0 - in which case yes, you will have to put a valid boot
config onto twed0

#2 - you could add the flag 'noauto' to ad0 from within fstab - this will
allow the system to boot without mounting the disk (alleviating the dreaded
single-user-mode). Use a startup script in /usr/local/etc/rc.d to then mount
the disk if available on bootup. I've done similar setups to this before
where we were using external USB drives for backup and weren't 100% sure
they'd always be connected in the case a server might be rebooted - worst
case, you'll end up with it not mounted, but the system will still be up at

Nathan Vidican

On Fri, Jan 22, 2010 at 12:53 PM, Billy Newsom <> wrote:

> I am doing a test run on a production server. It has 2 hard drives.
> ad0 (mounted on /disk250 in a single slice plus SWAP)
> twed0 (mounted on / /var /usr and a SWAP)
> The twed0 is a hardware mirror and my main drive.
> ad0 is just for backups.
> What the issue is, and you probably know where I'm heading. The boot
> process freezes if I remove the ad0 (to test a drive failure condition)
> It freezes after saying:
> BTX boot loader.... etc.
> FreeBSD/i386 bootstrap loader 1.1
> It spins for a second, then stops... unless I have ad0 in the computer.
> /boot/kernel/kernel text=0x7b03a0 data=0xcdee0 /
> And it never gets to the boot menu.
> So:
> 1. Should I put a new boot0config on the twed0 drive? If so do I boot from
> a CD to do that?
> I need to potentially do something also to my disk labels and my fstab so
> that I don't boot to single user mode if drive ad0 fails. I haven't done
> this exact type of thing before, so I am looking for a little help.
> my fstab:
> /dev/ad0s1b             none            swap    sw              0       0
> /dev/twed0s1b           none            swap    sw              0       0
> /dev/twed0s1a           /               ufs     rw              1       1
> /dev/ad0s1d             /disk250                ufs     rw      2       2
> /dev/twed0s1e           /tmp            ufs     rw              2       2
> /dev/twed0s1f           /usr            ufs     rw              2       2
> /dev/twed0s1d           /var            ufs     rw              2       2
> /dev/acd0               /cdrom          cd9660  ro,noauto       0       0
> I tried to read the MBR from the twed0 drive, and the program couldn't read
> it. The one from the ad0 drive is readable and I saved a copy of it.
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