Re: changes to the zfs boot (was: Re: git: 72a1cb05cd23 - main - rc(8): Add a zpoolupgrade rc.d script)

From: Mark Millard <marklmi_at_yahoo.com>
Date: Wed, 09 Nov 2022 20:10:18 UTC 
On Nov 9, 2022, at 11:58, Alexander Leidinger <Alexander@leidinger.net> wrote:

> Quoting "Patrick M. Hausen" <pmh@hausen.com> (from Wed, 9 Nov 2022 20:49:37 +0100):
> 
>> Hi,
>> 
>>> Am 09.11.2022 um 20:45 schrieb Alexander Leidinger <Alexander@leidinger.net>:
>>> But "zpool set feature@edonr=enabled rpool" (or any other feature not in the list we talk about) would render it unbootable.
>> 
>> Sorry, just to be sure. So an active change of e.g. checksum or compression algorithm
>> might render the system unbootable but a zpool upgrade never will? At least not intentionally? ;-)
> 
> If you mean "zpool upgrade", then no (modulo bugs). OpenZFS uses the feature flags instead of zpool upgrade.

I'm confused by that answer:

QUOTE of "man zpool-upgrade" output:
NAME
     zpool-upgrade – manage version and feature flags of ZFS storage pools
. . .
DESCRIPTION
     zpool upgrade
             Displays pools which do not have all supported features enabled
             and pools formatted using a legacy ZFS version number.  These
             pools can continue to be used, but some features may not be
             available.  Use zpool upgrade -a to enable all features on all
             pools (subject to the -o compatibility property).
. . .
     zpool upgrade [-V version] -a|pool…
             Enables all supported features on the given pool.
. . .
END QUOTE

zpool upgrade is a way of changing the feature flags, is it  not?

zpool upgrade also does not consider the loader's status, so far
as I know. If FreeBSD's kernel/world supports something that the
loader would reject, teh result is still rejection for booting.
As I understand, some folks ran into this for
com.delphix:head_errlog until an updated loader was available
and then installed.

===
Mark Millard
marklmi at yahoo.com