How to debug ZFS boot on UEFI?

Grzegorz Junka list1 at
Mon Jul 30 18:33:49 UTC 2018

On 30/07/2018 01:14, doug wrote:
> On Sun, 29 Jul 2018, Grzegorz Junka wrote:
>> Hi,
>> I've followed (more or less) this thread:
>> I have two disks nvd0 and nvd1 with three partitions on each: efi, 
>> freebsd-swap and freebsd-zfs. I've created the ZFS pool and installed 
>> FreeBSD manually (because on nvd1 I have also a few partitions used 
>> by Windows). On nvd1p1 I've created the hierarchy of files as 
>> outlined in the post:
>> efi/boot/BOOTx64.efi (copied from /boot/boot1.efi
>> boot/loader.rc (with the content as outlined in the post)
>> In UEFI boot menu I can see all partitions (Windows, UEFI shell, UEFI 
>> USB stick for 11.2, and the one I created). Booting from any 
>> partition works apart from the one I created - when that partition is 
>> selected UEFI shows a black screen for a second and then goes back to 
>> the boot menu.
>> How can I debug what's wrong?
>> Thanks
>> GrzegorzJ
> Did you try verbose boot? If you get nothing from that as far as I can 
> tell that means the code in the firmware did not find any thing to 
> transfer control to. I could never get beyond that point.

Thanks for your prompt response. I will try the rest of your advice when 
I get back to my computer, but in the meantime can you please tell me 
how to verbose boot?

As a side note, when I initially installed FreeBSD using mirror ZFS and 
guided installation the zdb label ended up on /dev/nvd0 device. When I 
installed the pool manually from shell it ended up on the /dev/nvd1p3 
device. I actually had problem with recognizing the correct pool in the 
installer until I force-cleared zfs label from nvd0.

I would like to try to move the zdb label from nvd1p3 to nvd0 to see if 
that makes any difference. Could be that the ZFS efi loader doesn't see 
ZFS properly until it's labelled on the main device rather than on a 
partition (I don't know much about ZFS labels). Is that possible?

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