Date: Sun, 12 May 2013 19:09:15 -0500 From: Larry Rosenman <ler@lerctr.org> To: freebsd-stable@freebsd.org Subject: Re: Reinstalling boot blocks on a ZFS-only system Message-ID: <f8c0516e9dc1ec3ad2ca3d86c0cb4176@webmail.lerctr.org> In-Reply-To: <20130512205837.GA69605@icarus.home.lan> References: <A6940C2F-17B4-4ECF-85B6-BA8CB335486E@distal.com> <20130512205837.GA69605@icarus.home.lan>
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On 2013-05-12 15:58, Jeremy Chadwick wrote:
> On Sun, May 12, 2013 at 04:50:46PM -0400, Chris Ross wrote:
>
> So, I've long known and it makes sense that when you're booted from a
> ZFS volume, you can't mess with the boot-loader. And, I know a few
> months ago I had a set of commands I would use when booted from a CD
> that would initialize the network and copy the "release/boot" from
> somewhere else so that I could install bootblocks and boot-loaders from
> more recent code. Sadly, I didn't _record_ those commands I was using.
>
> What do "people in the know" do when they want to update the bootblocks
> of a ZFS-boot system? Or, have too few people followed this path so
> far that they can boot UFS and do it with less difficulty?
>
> The command is "gpart bootcode", however I cannot be bothered to
> remember the syntax; I imagine it greatly depends on if you're using
> GPT
> vs. MBR, in addition to what your partition layout look like. Meaning:
> there is no "universal standard", it depends entirely on how you set
> your stuff up. But the command is definitely "gpart bootcode".
>
> Next, AFAIK there is no need to boot alternate media (CD etc.) to
> accomplish this.
>
> You may also need to set kern.geom.debugflags=0x10 to inhibit GEOM's
> "safety measure" / to permit writing to LBA 0; see GEOM(4) and search
> for the word "foot".
Assuming a freebsd-boot type partition, and GPT type partition scheme,
this is what I
use on my ZFS boot system:
$ cat bin/update_boot.sh
#!/bin/sh
for i in `seq 0 5`
do
echo Disk ${i}
gpart bootcode -b /boot/pmbr -p /boot/gptzfsboot -i 1 ada${i}
done
$
--
Larry Rosenman http://www.lerctr.org/~ler
Phone: +1 214-642-9640 (c) E-Mail: ler@lerctr.org
US Mail: 430 Valona Loop, Round Rock, TX 78681-3893
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