Ttgjyuk

APT seems to have an enduring blind-spot for computers which are not connected permanently to the internet. These days there are surely a ton of them, mostly laptops.

The general solution is unattended-upgrades. This is installed and run by default with a daily cron job. As a protection, anacron is also installed and run by default, and executes any cron jobs which were missed because the computer was turned off. So far so sensible.

BUT!

1. 
   

   Default unattended-upgrades config (/etc/apt/apt.conf.d/50unattended-upgrades or similar) requires the following to be set, else upgrades risk being skipped:

   
   
   

   Unattended-Upgrade::OnlyOnACPower "false";
   Unattended-Upgrade::Skip-Updates-On-Metered-Connections "false";
   

   
   



2. More importantly, anacron, like cron, runs jobs whether or not an internet connection is available! This is clearly a major design bug for non-server Ubuntu, since personal computers are not always connected permanently. With default config, on a nomadic laptop, unattended-upgrades will simply fail much of the time.

(Perhaps there needs to be a separate class of cron job which waits for a network connection until executing. Or failed cron.daily jobs could be switched to cron.hourly until they execute successfully.)

One practical solution is a systemd unit file to execute unattended-upgrades as a user script after the network comes online. But it will only run once per boot.

What is the optimal solution? Does anyone know if there are plans to fix this with a new package or a config improvement?

If connecting to internet with network-manager, the current default on Ubuntu, then create a dispatcher script to launch unattended-upgrades after connecting to the network:

sudo touch /etc/NetworkManager/dispatcher.d/20-myconnectionscript
sudo chmod +x /etc/NetworkManager/dispatcher.d/20-myconnectionscript

In 20-myconnectionscript:

#!/bin/sh

if [ "$2" = "up" ];
 # only proceed if unattended-upgrades was last run more than a day ago
 ELAPSEDSINCEUU=$(($(date +%s) - $(date +%s -r /var/lib/apt/periodic/unattended-upgrades-stamp)))
 if [ $ELAPSEDSINCEUU -gt 86400 ]; then
 /usr/bin/unattended-upgrades
 fi
fi