I've set up unattended-upgrade on an Ubuntu 14.04.1 server. It has installed the kernel .41 over .40 yesterday at 4:10. Automatic reboot is configured for 3:00, so it should have rebooted last night. But it didn't.
Today, it installed another kernel version .43. Still the /var/run/reboot-required file does not exist, and the mail from unattended-upgrade doesn't contain any notice of a required reboot. So I don't expect the scheduled reboot to work tomorrow and the new kernel still won't be applied.
What's the issue here? Why doesn't that work as configured?
APT::Periodic::Update-Package-Lists "1"; APT::Periodic::Unattended-Upgrade "1";
Unattended-Upgrade::Automatic-Reboot "true"; Unattended-Upgrade::Automatic-Reboot-Time "03:00";