Getting ZFS pools back.

Jan Knepper jan at
Sun Apr 29 18:31:35 UTC 2018

On 04/29/2018 14:21, Warner Losh wrote:
> On Sun, Apr 29, 2018 at 11:57 AM, Jan Knepper <jan at 
> <mailto:jan at>> wrote:
>     On 04/29/2018 13:27, Willem Jan Withagen wrote:
>         Trouble started when I installed (freebsd-update) 11.1 over a
>         running 10.4. Which is sort of scarry?
>     This does sounds 'scary' as I am planning to do this in the (near)
>     future...
>     Has anyone else experienced issues like this?
>     Generally I do build the new system software on a running system,
>     but then go to single user mode to perform the actual install.
>     I have done many upgrades like that over 18 or so years and never
>     seen or heard of an issue alike this.
> 11.x binaries aren't guaranteed to work with a 10.x kernel. So that's 
> a bit of a problem. freebsd-update shouldn't have let you do that either.
The process I have used so far is to svnup, build, reboot...
> However, most 11.x binaries work well enough to at least bootstrap / 
> fix problems if booted on a 10.x kernel due to targeted forward 
> compatibility. You shouldn't count on it for long, but it generally 
> won't totally brick your box. In the past, and I believe this is still 
> true, they work well enough to compile and install a new kernel after 
> pulling sources. The 10.x -> 11.x syscall changes are such that you 
> should be fine. At least if you are on UFS.
> However, the ZFS ioctls and such are in the bag of 'don't specifically 
> guarantee and also they change a lot' so that may be why you can't 
> mount ZFS by UUID. I've not checked to see if there's specifically an 
> issue here or not. The ZFS ABI is somewhat more fragile than other 
> parts of the system, so you may have issues here.
> If all else fails, you may be able to PXE boot an 11 kernel, or boot 
> off a USB memstick image to install a kernel.
> Generally, while we don't guarantee forward compatibility (running 
> newer binaries on older kernels), we've generally built enough forward 
> compat so that things work well enough to complete the upgrade. That's 
> why you haven't hit an issue in 18 years of upgrading. However, the 
> velocity of syscall additions has increased, and we've gone from 
> fairly stable (stale?) ABIs for UFS to a more dynamic one for ZFS 
> where backwards compat is a bit of a crap shoot and forward compat 
> isn't really there at all. That's likely why you've hit a speed bump here.
I have not closely looked at the procedures outlined in 
/usr/src/UPDATING for 11.x. But do I read correctly that performing a 
buildworld, buildkernel, then installworld and reboot to update from 
10.4 to 11.x does not work?


Jan Knepper

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