alappe/cookbook-openntpd — pull request #1 by klamontagne (2014-07-03 15:24:18+00:00)
Title: Remove ntpd, reload apparmor

"openntpd" replaces "ntp" on Ubuntu.

dpkg will fail on post-install of openntpd with:
Starting openntpd: /etc/openntpd/ntpd.conf: Permission denied

if the ntp apparmor profile is still applied.
Even after the ntp package purge, it's still in the cache.