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Unattended Upgrades

The purpose of unattended-upgrades is to keep the computer current with the latest security (and other) updates automatically.

If you plan to use it, you should have some means to monitor your systems, such as installing the apt-listchanges package and configuring it to send you emails about updates. And there is always /var/log/dpkg.log, or the files in /var/log/unattended-upgrades/.

As of Debian 9 (Stretch) both the unattended-upgrades and apt-listchanges packages are installed by default and upgrades are enabled with the GNOME desktop. Rudimentary configuration is accessible via the "Software & Updates" application (software-properties-gtk).

To install these packages, run the following command as root:

The default configuration file for the unattended-upgrades package is at /etc/apt/apt.conf.d/50unattended-upgrades. The defaults will work fine, but you should read it and make changes as needed.

This section controls which packages are upgraded:

You should at least uncomment the following line:

Automatic call via /etc/apt/apt.conf.d/20auto-upgrades

To activate unattended-upgrades, you need to ensure that the apt configuration stub /etc/apt/apt.conf.d/20auto-upgrades contains at least the following lines:

The file /etc/apt/apt.conf.d/20auto-upgrades can be created manually or by running the following command as root:

Or non-interactively by running:

Automatic call via /etc/apt/apt.conf.d/02periodic

Alternatively, you can also create the apt configuration file /etc/apt/apt.conf.d/02periodic to activate unattended-upgrades:

Below is an example /etc/apt/apt.conf.d/02periodic:

Manual run (for debugging)

To aid debugging you may need to run unattended-upgrades manually thus:

sudo unattended-upgrade -d

See Also

apt-listchanges

Below is an example configuration file for apt-listchanges, /etc/apt/listchanges.conf:

Modifying download and upgrade schedules (on systemd)

Because Debian is using the  systemd  system, it has timers defined for APT use, these files are provided by the apt package.
The relevant files are:

The canonical steps to create and edit these overrides for these settings are for downloads

Here is an example of how to override the download time to 1AM by adding the following via sudo systemctl edit apt-daily.timer :

   1 [Timer]
   2 OnCalendar=
   3 OnCalendar=01:00
   4 RandomizedDelaySec=0

Line #2 above is needed to reset (empty) the default value shown below in line #5.
Line #4 above is needed to prevent any random delays coming from the defaults.

The current default values for downloads are /lib/systemd/system/apt-daily.timer is (at moment of this writing):

   1 [Unit]
   2 Description=Daily apt download activities
   3 
   4 [Timer]
   5 OnCalendar=*-*-* 6,18:00
   6 RandomizedDelaySec=12h
   7 Persistent=true
   8 
   9 [Install]
  10 WantedBy=timers.target