unattended-upgrades not running, /etc/cron.daily/apt missing

I have automatic-upgrades installed and configured, but it never seems to run, because there are always security updates waiting to be installed when I check.

https://help.ubuntu.com/community/AutomaticSecurityUpdates seems to imply that /etc/cron.daily/apt is the mechanism by which automatic-upgrades works. However, /etc/cron.daily/apt is missing.

dpkg -S indicates that apt owns that file.

Am I correct that a missing /etc/cron.daily/apt would prevent unattended-upgrades from running? If so, how would I create it?

(I'm not the only one with this problem, as evidenced by this Ubuntu Forums post, which unfortunately doesn't have a solution.)

Solution 1:

Try

apt-get install cron-apt

for this file

Solution 2:

As far as I can tell, the file is missing from the .deb - a packaging error. I have not yet worked out how to get this raised to the attention of the packagers