Moving boot disk - does not seem easy?

Robert Huff roberthuff at
Thu Sep 12 23:33:12 UTC 2019

Karl Denninger writes:
>  On 9/12/2019 16:26, james wrote:
>  > I had thought that this would be straightforward but it seems not.
>  >
>  > I have a freebsd 12 system, UFS boots /ada0p2.  Mounts some ZFS
>  > partitions and I'm away.
>  >
>  > I add a new PCIe card with a SATA SSD, and it grabs ada0.
>  >
>  > I want to move my boot to the SSD, not least because the boot priority
>  > now favours it as ada0, and I had to manually boot ada1p2.
>  >
>  > There's not much on ada1p2 now, but I want the new ada0p2 to be
>  > smaller, so dd is not attractive.
>  >
>  > What's the easiest way to set ata0 to be much like ada0p2 was (given
>  > that I booted from ada1p2)?
>  >
>  > Ideally I'd like boot and swap etc set up as well, which I kinda did
>  > already with sade.
>  >
>  > I already had the issue with freebsd-install/MANIFTEST missing and did
>  > a basic install to ada0, but it seems a bit naff to unmount all my ZFS
>  > mountpoints just to tar across all the rest of it.
>  >
>  > Any pointers?
>  >
>  I've done this many times and it's very easy.
>  Look at the old disk (e.g. "gpart ada1" and friends) so as to get the
>  proper partition settings (e.g. sizes, etc)
>  Use gpart to set up the NEW disk with the same basic configuration
>  (slice types, etc.) -- it is, of course, ok to change the sizes --
>  it's just important that the data on the old disk fits.

	Use gpart to label the new disk - call it, say, "root".
	<rest of copying instructions deleted>
	In fstab, replace however you currently mount / with:

/dev/gpt/root	/		ufs		rw		1	1

	changing "ufs" to "zfs" if appropriate.
	Power down system; unhook old drive; start system.  Things should
Just Work.


				Robert Huff

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