Peter Ankerstål on the -stable mailing list reports a failure to boot after using freebsd-update to upgrade from 10.3-RELEASE to 11.0-RELEASE https://lists.freebsd.org/pipermail/freebsd-stable/2016-October/085799.html The issue is caused by EC2 hanging on an attempt to read past the end of the disk The issue was introduced in r297629 (6 months ago), but was not caught because most installs are 4k aligned by the installer, and on most hardware, a read past the end of the disk returns and error, which is silently ignored and booting continues normally. For EC2, newer snapshots and images use a newer disk layout that is 4k aligned, so avoided this issue. Only older instances being upgraded to 11.0 encountered the problem.
A commit references this bug: Author: allanjude Date: Tue Oct 4 16:33:03 UTC 2016 New revision: 306677 URL: https://svnweb.freebsd.org/changeset/base/306677 Log: GELIBoot may attempt to read past the end of the disk Usually there is some slack after the last partition due to 4k alignment In the 10.3 EC2 images, there was not. EC2 seems to hang if you try to read past the end of the disk in the loader, resulting in an unbootable instance after upgrading to 11.0 PR: 213196 Reported by: Peter Ankerstal <peter@pean.org> Tested by: cperciva Reviewed by: tsoome MFC after: 3 days Sponsored by: ScaleEngine Inc. Differential Revision: https://reviews.freebsd.org/D8144 Changes: head/sys/boot/geli/geliboot.c
A commit references this bug: Author: allanjude Date: Sat Oct 8 00:01:07 UTC 2016 New revision: 306834 URL: https://svnweb.freebsd.org/changeset/base/306834 Log: MFC: r306677 GELIBoot may attempt to read past the end of the disk PR: 213196 Relnotes: yes Sponsored by: ScaleEngine Inc. Changes: _U stable/11/ stable/11/sys/boot/geli/geliboot.c
The Errata Notice for this bug has been published: https://www.freebsd.org/security/advisories/FreeBSD-EN-16:18.loader.asc It is now safe to upgrade with freebsd-update