Re: making a disk/slice bootable

I haven't used recoverdisk.  If you're going to mirror, use one of the other things I mentioned.  gmirror is low-impact and easy enough to use and supported by the various boot loaders.

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…thanks for this. 
> 
> So a further Q…if 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 <mailto: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
> >
> > From 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 <mailto:freebsd@gushi.org>> wrote:
> > >
> > >
> > >
> > >> On Sep 1, 2022, at 16:41, paul beard <paulbeard@gmail.com <mailto: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/ <http://www.paulbeard.org/>