Changing trains; Downgrade back to freenas

[enilla]

Sooo, I was doing some admin stuff on my freenas server at home, aiming to make and connect an SMB share. Should be straight forward, but wasn't, so after getting annoyed, and wanting to ask for help, I checked for updates first, because update before asking help right, or it's going to be the #1 reply? So I updated to the newest freenas version (11.3 I think?). Another 2 hours of trial and error, still not working. So now I was quiet annoyed. And yes, that's the time to go to bed, and continue the next day... Yeah... I didn't.
So I was like "ah, theres also a newer train available!" And I read about FreeNas continuing as TrueNas quiet a while ago, and the available version was 12.0, sounds like a stable release to me, or at least it does at 1AM. So yes I switched to the 12.0 train, assuming it's a stable one. Tried fiddling some more, but couldn't get my SMB share running.
Now the next day I've done some more research, and am kinda figuring out that 12.0 was not the stable release I assumed it to be. Or even a beta... Oops...

So before continuing my journy to get the bloody SMB share working, I figure I first have to salvage my installation to get back to a stable version. I guiss I could always try a fresh install of freenas, and import my pool. But I did a "pool upgrade" in the new version of truenas, as I got a message telling me that that was a thing, and why not upgrade a pool in a stable release >.> So my first question I guess is was this pool upgrade a feature from the newest freenas, or is it from truenas core? In other words, will a downgrade be possible at all?

Another question is whether this downgrade would be possible by changing trains in the GUI (haven't found it) or maybe by doing a manual update?

And if downgrading with my current pool is risky/impossible, what are the risks in running truenas core till it's stable?

 

[Yorick]

Yup, you're stuck. There are multiple feature flags in 12.0 that are not backwards-compatible. They are probably not read-only compatible. See https://www.ixsystems.com/community/threads/zfs-feature-flags-in-freenas.63536/ and http://www.open-zfs.org/wiki/Feature_Flags.

TrueNAS Core 12 Nightly is "reasonably stable" in my testing. There is some behavior around VMs and changing jail parameters that is being worked on. SMB works, jails work. I have no way of testing NFS or iSCSI.

You can't move back to another train from Nightly, though. Keep the 11.3 boot environment, mark it as something you don't ever want to be deleted. Once 12 Alpha is out, you are probably better off exporting your pool, booting back into 11.3 environment - your pool may be MIA and may have to be re-imported once you are on 12 again - and moving to 12 Alpha, then importing your pool. Moving from Alpha to Beta to Release is supported, unlike Nightly.

Edit: I am reading into these "not read only compatible" flags, and I found hole_birth, which is not read-only compatible and "This feature becomes active as soon as it is enabled and will never return to being enabled." If I read this right, that means your pool cannot be read in anything below TrueNAS 12.
Edit 2: Export, 11.3, 11.3->12 Alpha, import out of an abundance of caution. No doubt someone with more ZFS experience will be along telling me I am paranoid, and that "11.3, 11.3->12 Alpha, possibly import" is sufficient. Another possible path would be "12 Nightly config backup; reinstall 12 Alpha; restore config"
Edit 3: I opened an enhancement request for a more stringent warning. https://jira.ixsystems.com/browse/NAS-105779

You're in it now. Take that as a lesson learned to leave ZFS Feature Flags alone until you are 100% absolutely certain you'll never want to use that pool in anything "lower".

 

[Ericloewe]

I found hole_birth

Yes, but hole_birth is ancient. It's been supported since who-knows-when.

My 5-minute research on TrueNAS 12.0 feature flags: https://www.ixsystems.com/community/threads/zfs-feature-flags-in-freenas.63536/post-579136

IIRC, there's like half a dozen in there that break backward compatibility immediately.

 

[anodos]

Maybe you can explain the SMB problem in more detail. If it's a permissions issue then it won't be fixed by jumping around with versions, but it can usually be fixed with some minor intervention.

 

[Yorick]

Yes, but hole_birth is ancient. It's been supported since who-knows-when.

Oh yes, you are right. That might be good news, in that the pool will at least stay read-only compatible.

 

[enilla]

Just an update: I installed freenas 11.3 on a new bootdrive, same machine. The pool was not readable, at least not using the UI, not sure if fiddling in the CLI would help. But anyway, I made a new pool in 11.3, rebooted the machine using the truenas boot drive, and now both pools are readable. So in 12.0 I have moved my pool's content from the old pool, to the new pool (made same datasets and used cp -a to copy the content)
Now w.r.t. the smb issue. It's fixed in 11.3, but I think the thing that fixed it was a reïnstall. Did the same thing for making a test dataset and smb share. So no ideas what the issue was. I guiss that will be forever a mistery...