Date: Sun, 12 May 2013 22:20:26 -0400 From: Chris Ross <cross+freebsd@distal.com> To: Jeremy Chadwick <jdc@koitsu.org> Cc: "freebsd-stable@freebsd.org" <freebsd-stable@freebsd.org> Subject: Re: Reinstalling boot blocks on a ZFS-only system Message-ID: <28B5181C-E185-40E5-90EC-9600297BE590@distal.com> 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 May 12, 2013, at 16:58 , Jeremy Chadwick <jdc@koitsu.org> wrote:
> 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".
In the past, I've found I've been unable to install all of the bootblocks if I
boot from the ZFS root. When booting from a cd, the basic:
gpart bootcode -p ${bootdir}/zfsboot ${disk}
dd if=${bootdir}zfsloader of=/dev/${disk}a bs=512 oseek=1024 conv=notrunc,sync
works. But, if I boot from ZFS, then I can't dd anything into the front of the
drives. Right now, the problem after booting from the CD, is trying to mount
a read/write filesystem (mfs, or the like) so that I can scp the bootblocks onto the
system and install them. BUt, I eventually found the command I'd lost. so I
think I'm alright. Thanks...
- Chris
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