mounting from zfs:zroot/ROOT/default failed with error 45

Mike Tancsa mike at
Mon Apr 8 14:26:46 UTC 2019

On 4/8/2019 6:21 AM, CyberLeo Kitsana wrote:
>>> Actually, I wonder if the issue is that I am doing the zpool create on a
>>> RELENG_12 box.... So when I try and boot that zpool that was freshly
>>> created on RELENG_12 with a RELENG_10 kernel, I am running into issues.
>> It does seem to be a zfs version issue which kinda makes sense. If I
>> create the zfs image on a RELENG10 vm it works.  The only issue is that
>> its quite slow to do on the VM as its a LOT of disk IO.  Is there a way
>> to create an older version of a zfs file system on a newer version of
>> FreeBSD so I can get the best of both worlds ?
> Yes. Take a look at the differences in the feature flags available on 10
> and 12, and, during pool creation, explicitly set disabled the ones that
> are not present on 10.
> I don't have any 10 nor 12 boxen available to me, but the one I recently
> upgraded from 10 to 11 shows the following feature flags were added (and
> never enabled on my pool):
> sha512
> skein
> device_removal
> obsolete_counts
> zpool_checkpoint
> 12 may add more.
Thanks for the hints!  Looking at a pool created on 12 vs the version I
am trying to work with from 10, in terms of features referenced,

 feature at large_dnode does not exist

and a bunch that do are turned off.

 diff old new
< feature at sha512                 disabled                       local
< feature at skein                  disabled                       local
< feature at device_removal         disabled                       local
< feature at obsolete_counts        disabled                       local
< feature at zpool_checkpoint       disabled                       local
< feature at spacemap_v2            disabled                       local
> feature at large_dnode            enabled                        local
> feature at sha512                 enabled                        local
> feature at skein                  enabled                        local
> feature at device_removal         enabled                        local
> feature at obsolete_counts        enabled                        local
> feature at zpool_checkpoint       enabled                        local
> feature at spacemap_v2            active                         local

However, there doesnt seem to be a way to create the pool with features
disabled. The man page seems to imply that as well, at least on FreeBSD
? And trying to set it implies that as well.

0(nfs2)# zpool create -f -o altroot=/mnt2 -O "canmount=off" -o
'feature at spacemap_v2=disabled' -m none zroottest /dev/md0p3
cannot create 'zroottest': property 'feature at spacemap_v2' can only be
set to 'enabled'


Mike Tancsa, tel +1 519 651 3400 x203
Sentex Communications, mike at
Providing Internet services since 1994
Cambridge, Ontario Canada   

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