If you're just cloning = disk to similar disk with rsync, you should not need to do this more = than once, unless maybe if you upgrade your system. Normal = freebsd-update upgrades do not generally touch the boot blocks. = The best advice I can give is "test this BEFORE you need it". = Rip your primary drive out and see if you still boot.

For a = lightweight system, even zfs mirroring is okay, but it does use some ram = for caching and the like, so I wouldn't try it with a tiny embedded = box.

-Dan

On Sep = 1, 2022, at 17:47, paul beard <paulbeard@gmail.com> wrote:

yeah, I was pretty sure I was using the wrong tool=E2=80=A6than= ks for this.

So a further Q=E2=80=A6if I = continue to use recoverdisk from ports to mirror my boot disk to a copy, = is it best practice to do this on the mirror after the mirroring is = completed? For all I know there is a far better way to do that but this = is a FreeBSD 11 system (!) that has just been doing its thing for some = years. So it worked (more or less) when it was set up. A backup you = can't use isn't much use, as I have learned (again, I expect).

On Thu, Sep 1, 2022 at 5:20 PM Dan Mahoney = <freebsd@gushi.org> wrote:
>
> Fdisk is for old-school partitions (where disks had only = 1-4 primary partitions, and then subdivided those partitions into = "slices" (bsdlabel).
>
> I'm pretty = sure the command you're looking for is:
>
> gpart bootcode -b /boot/pmbr -p /boot/gptboot -i 1 = ada1
>
> In english, this says:
>
> * Stick the "protective master boot = record" on the root of the disk (/boot/pmbr)
> * Write = a partition boot label from the file specified...
> * = to this indexed partition (-i 1)
> * ...on ada1
>
> =46rom there, you may need to tell = the stage 0 loader where to find your next bootable partition on the = next boot() prompt.
>
> -Dan
>
>
> > On Sep 1, = 2022, at 16:44, Dan Mahoney <freebsd@gushi.org> wrote:
> >
> >
> >
> >> = On Sep 1, 2022, at 16:41, paul beard <paulbeard@gmail.com>= wrote:
> >>
> >> I have = been mirroring the virtual disk in a FreeBSD vm for a couple of years = and the main disk got corrupted. The mirrored disk doesn't boot, says it = can't find a kernel, so I think I missed out on an additional step, = writing an MBR or boot sector, perhaps.
> >>
> >> The files are all there if I mount them from a = VM with FreeBSD.I assume there is a way to make a mountable disk = bootable. fdisk and gpart are available but it's been a long time = since I messed around with those.
> >
> > Let's start with the obvious: Can you post your = disk layout? Mirrored how? Gmirror/ZFS/Hardware = raid/etc? MBR or Gpart?
> >
> = > What commands have you tried thusfar?
> >
> > What does the boot so far look like (i.e. are you = hitting the stage 0 boot loader, and getting the loader prompt?)
> >
> > More info required, please, = but this sounds very fixable.
> >
> = > -Dan
>

--
Paul Beard / www.paulbeard.org/
=