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From: Brian Bobowski <bbobowski@cogeco.ca>
To: Ewald Jenisch <a@jenisch.at>, freebsd-questions@freebsd.org
Date: Mon, 6 Oct 2003 08:54:36 +0000
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Subject: Re: Multiple kernels on one machine?
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On October 6, 2003 12:11 pm, Ewald Jenisch wrote:
> Hi,
>
> I'm currently in the process of upgrading my kernel (5.1). Afaik, every
> time one installs a new kernel with "make installkernel" the old
> /boot/kernel is moved to /boot/kernel.old thus overwriting the old
> /boot/kernel.old.
>
> In order to keep a working kernel: Is it possible to *keep* an old
> kernel by copying, say /boot/kernel.old to e.g. /boot/mykernel and then
> via the boot-menu starting this kernel by
>
> unload
> boot mykernel
>
> ??
>
> If yes, can I simply copy (e.g. via tar | tar xpf..) the old kernel
> directory to a new name or is there anything else I should consider?
>
> TIA for your help
> -ewald

As far as I know, this is not only possible, but recommended in the Handbook 
directions for building new kernels. That way, if you've done several 
rebuilds, you know you've got a working kernel around.

I didn't find much in the way of specifics in the handbook, so the process 
might be as simple as you say(though I myself haven't yet figured out how to 
pipe a tar into an untar).