systemd 222 on Fedora 23 suffers from a rather annoying issue when using systemd-nspawn, reported on https://github.com/systemd/systemd/issues/376 (fixed upstream in later versions). Basically, if you run "systemctl daemon-reload" (which happens implicitly when you install new packages or update the system), machined loses track of the machines. So you have to do a "systemctl restart systemd-nspawn@MACHINE" for all of the machines that were running.
Created attachment 1113381 [details] Backport of 49f3fffd94591bdf2bd6c2233a9300daeab79566 I propose to backport 49f3fffd94591bdf2bd6c2233a9300daeab79566 (https://github.com/poettering/systemd/commit/49f3fffd94591bdf2bd6c2233a9300daeab79566) on f23. This attachment is a patch against the f23 branch of the systemd git fedora package, that adds the 49f3fffd94591bdf2bd6c2233a9300daeab79566 patch to the list. I've tested the generated package and it fixes the issue.
http://pkgs.fedoraproject.org/cgit/rpms/systemd.git/commit/?h=f23&id=64a629fdb1043318deef00b2cc5c7ee0e2908aaf
systemd-222-13.fc23 has been submitted as an update to Fedora 23. https://bodhi.fedoraproject.org/updates/FEDORA-2016-3d6ff41417
systemd-222-13.fc23 has been pushed to the Fedora 23 testing repository. If problems still persist, please make note of it in this bug report. See https://fedoraproject.org/wiki/QA:Updates_Testing for instructions on how to install test updates. You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2016-3d6ff41417
systemd-222-13.fc23 has been pushed to the Fedora 23 stable repository. If problems still persist, please make note of it in this bug report.