understood!
Because TrueNAS Scale is considered an "appliance" not just another linux distribution. When you go tinkering under the hood you stand a very good chance of breaking things as you have discovered. Your only option at this point is to do a fresh install of TrueNAS and upload a saved copy of your config. You do have a backup of your configuration correct?
zfs compatibility flags should prevent this now; even if someone manually zpool upgrade's the boot pool it shouldn't enable any features that will break GRUB.
Oh nice, I think I missed that on my initial skim, I do see that it's mentioned on a prior page.
It doesn't, for the boot pool. You also can't upgrade the boot pool through the GUI. So if you're using the system as it's intended to be used, you won't have this problem. Unfortunately, there's a lot of bad information out there (including in this very forum) telling people to run things like
zpool upgrade -a at the shell, which will result in exactly this problem.Thanks for pointing out there is a GUI for it now. You're absolutely right, if one sticks to the GUI, can't cause the problem. I'd been doing it on the CLI since I started using FreeNAS in 2012.
Upgrading the ZFS version/features of the pool has always been in the GUI, at least as far back as FreeNAS 9.3, which is now ten years old. There's never been a need to do it at the CLI.
