Re: using GPT support in BIOS boot

[Jeff Rizzo <riz%tastylime.net@localhost>]

On 1/5/11 8:27 PM, Jonathan A. Kollasch wrote:
> Hi,
>
> Just a quick summary of how to use the new GPT support in the x86
> boot stack.  (sysinst doesn't understand this yet.)
>
> # gpt create wd1
> # gpt add -b 64 -s 2097152 wd1
> # dkctl wd1 addwedge wd1_1 64 2097152 ffs
> # newfs -O2 dk0
> # installboot /dev/rdk0 /usr/mdec/bootxx_ffsv2
> # gpt biosboot dk0
> # mount /dev/dk0 /mnt
> # cp -p /usr/mdec/boot /mnt/
>
> That's the basics, you'll want a kernel and root file system
> on dk0 too to completely test this out.
>
> Features:
> - You can boot from a root partition at or above 2TiB if your BIOS
>    properly supports block addresses above the 32-bit barrier.
>
> Limitations:
> - The GPT MBR only supports 128 partitions (the default and minimum).
> - "/boot" only understands the first 26 partition entries (hdX[a-z]).
>
> Thanks to Mike M. Volokhov for his work during GSoC 2009 that
> made this possible.
>
>         Jonathan Kollasch

First off, thanks a ton for getting this done.  I just tried it, and it 
works great.

One thing that I was curious about: whether it's important to start the 
partition at 64 like you did.  The answer: apparently not.  I just let 
gpt add do its default thing, and it started at 34 and worked fine.

This is really, really good stuff.

+j