Eager sysadmins like to upgrade their ZFS pool versions and then reboot. This can cause problems if one doesn't update the gpart bootcode. I presently have a workstation I can't boot because I didn't realize I needed to do this. Putting this information in UPDATING for every relevant feature flag change would save people like me rather a lot of time and frustration. Fix: A mailing list post (http://lists.freebsd.org/pipermail/freebsd-current/2014-January/047639.html) suggests upgrading the bootcode should be sufficient. This needs to get into UPDATING because foregoing this step leaves a system not bootable. How-To-Repeat: Install 10-RELEASE with ZFS root. Upgrade to 10-STABLE after the new feature flags from Delphix went in. Reboot. Witness gptzfsboot being unable to import the bootpool.
Responsible Changed From-To: freebsd-bugs->freebsd-fs Over to maintainer(s).
Seems unnecessary since 'zpool upgrade' already spits out exactly what you need to do with an appropriate warning.
Created attachment 147531 [details] Untested patch that adds the missing bootcode upgrade warning I've just had the same problem after upgrading my bootpool on 10-stable. I used "zpool upgrade -a". I was already on pool version 5000; only some feature flags were added. The problematic feature flags not recognized by the bootloader were "com.delphix:hole_birth" and "com.delphix:embedded_data". I was aware of the "gpart bootcode" dance but "zpool upgrade -a" definitely showed no message so I assumed it was safe to reboot without upgrading the bootloader. I've looked at the zpool code and it seems that in the case of "zpool upgrade -a" the bootcode upgrade warning may not be displayed. I've attached a patch that should fix it (untested, but it compiles).
Fixed in head by: http://svnweb.freebsd.org/changeset/base/271934
A commit references this bug: Author: smh Date: Wed Sep 24 09:59:49 UTC 2014 New revision: 272063 URL: http://svnweb.freebsd.org/changeset/base/272063 Log: MFC r271934: Output boot code warning when zpool upgrade -a is used to add features. PR: 188328 Approved by: re (marius) Sponsored by: Multiplay Changes: _U stable/10/ stable/10/cddl/contrib/opensolaris/cmd/zpool/zpool_main.c