Comment 37 for bug 1686470

An annoyance about this change is that it reuses the apt-daily.timer for only download and lets the upgrade be triggered by a new apt-daily-upgrade.timer.

Systems using apt <1.2.24 which were sensitive to the upgrade point of time would typically have overridden the apt-daily.timer to happen at a fixed time. After upgrade to apt 1.2.24 those systems would still have apt-daily.timer run at the time chosen by the administrator but triggering /usr/lib/apt/apt.systemd.daily update to download packages would make it bail out (as the unattended-upgrades 0.90-ubuntu0.7 which introduced the --download-only option is not a SRU). But upgrades, and effectively also download until a manual upgrade of unattended-upgrades, would happen at the default apt-daily-upgrade.timer time (06:00+random(60m)).

Security updates that warps carefully scheduled and important system events like this leaves the impression that administrators are not in control of their machines.