backup drive bootabel

Matthew Seaman m.seaman at
Wed Nov 12 10:21:13 PST 2003

On Wed, Nov 12, 2003 at 09:20:14AM -0800, Noah wrote:

> I will consider it.  in the mean time can somebody explain to me how to make
> the 2nd drive bootable.  I have seen many different ways to do this.  can you
> direct me to the most optimal.  I want to place a boot section that has no
> menu and no options.  just load teh kernel and go.

These are SCSI drives? So one disk is da0 and the other is da1.  

There's two ways to work this:

i) Make the 2nd disk an identical copy to the 1st one.  In this case
should the 1st drive go AWOL, you would have to open the case and
either remove the first drive or modify the jumpering on the disks to
swap their order on the bus.  You will need to mark the FreeBSD slice
bootable in the disk partition label by running:

    # boot0cfg -B -b /boot/mbr -s 1 da1

So long as the slice tables and disklabels on da0 and da1 are pretty
much the same, either disk should boot up smoothly.

ii) Set up the system so that you can boot from either disk at will,
without having to fiddle around with the hardware at all. This means
that the settings on the two drives cannot be exactly the same:
specifically the /etc/fstab file on each disk should reference the
filesystems on the same disk: da0 on da0 or da1 on da1.

Now, you can boot from either disk by interrupting the boot process by
hitting a key while the spinning cursor is showing (| / - \ ...)
[That's before the system loads the kernel and prints the message
about the 10s countdown] -- it can be tricky to catch the system at
this stage especially if booting from a fast device.

At the boot: prompt, type:


to boot from da0, or


to boot from da1.

If you take this route, you may find it more convenient to set up the
machine for dual-boot with the slightly unusual configuration of two
copies of the same OS.
In this case you'll need to install the FreeBSD boot block, which will
mean that you get a prompt at boot time where you can choose which
disk to boot from, but unless you start hitting the function keys,
after a short delay the system will carry on an boot up from the same
disk as the previous boot:

    # boot0cfg -B -b /boot/boot0 da0
    # boot0cfg -B -b /boot/boot0 da1



Dr Matthew J Seaman MA, D.Phil.                       26 The Paddocks
                                                      Savill Way
PGP:         Marlow
Tel: +44 1628 476614                                  Bucks., SL7 1TH UK
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