Comment 23 for bug 1778219

Verified 1.1ubuntu1.18.04.7 on Bionic:

...
root@uu-shutdown-test:~# service unattended-upgrades status
● unattended-upgrades.service - Unattended Upgrades Shutdown
   Loaded: loaded (/lib/systemd/system/unattended-upgrades.service; enabled; vendor preset: enabled)
   Active: active (running) since Wed 2018-11-28 16:06:14 UTC; 1s ago
     Docs: man:unattended-upgrade(8)
 Main PID: 230 (unattended-upgr)
    Tasks: 2 (limit: 4915)
   CGroup: /system.slice/unattended-upgrades.service
           └─230 /usr/bin/python3 /usr/share/unattended-upgrades/unattended-upgrade-shutdown --wait-for-signal

Nov 28 16:06:14 uu-shutdown-test systemd[1]: unattended-upgrades.service: Failed to reset devices.list: Operation not permitted
Nov 28 16:06:14 uu-shutdown-test systemd[1]: Started Unattended Upgrades Shutdown.
root@uu-shutdown-test:~# vi /etc/apt/sources.list
root@uu-shutdown-test:~# apt update
Hit:1 http://archive.ubuntu.com/ubuntu bionic InRelease
Get:2 http://security.ubuntu.com/ubuntu bionic-security InRelease [83.2 kB]
Get:3 http://archive.ubuntu.com/ubuntu bionic-updates InRelease [88.7 kB]
Get:4 http://archive.ubuntu.com/ubuntu bionic-backports InRelease [74.6 kB]
Fetched 247 kB in 0s (505 kB/s)
Reading package lists... Done
Building dependency tree
Reading state information... Done
6 packages can be upgraded. Run 'apt list --upgradable' to see them.
root@uu-shutdown-test:~# echo 'Unattended-Upgrade::InstallOnShutdown "true";' > /etc/apt/apt.conf.d/51unattended-upgrades-on-shutdown
root@uu-shutdown-test:~# echo 'Unattended-Upgrade::Allowed-Origins:: "${distro_id}:${distro_codename}-updates";' > /etc/apt/apt.conf.d/51unattended-upgrades-updates-too
root@uu-shutdown-test:~#
root@uu-shutdown-test:~# apt install snapd=2.32.5+18.04
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following package was automatically installed and is no longer required:
  libfreetype6
Use 'apt autoremove' to remove it.
The following packages will be DOWNGRADED:
  snapd
0 upgraded, 0 newly installed, 1 downgraded, 0 to remove and 6 not upgraded.
Need to get 12.2 MB of archives.
After this operation, 860 kB disk space will be freed.
Do you want to continue? [Y/n]
Get:1 http://archive.ubuntu.com/ubuntu bionic/main amd64 snapd amd64 2.32.5+18.04 [12.2 MB]
Fetched 12.2 MB in 0s (75.4 MB/s)
dpkg: warning: downgrading snapd from 2.34.2+18.04 to 2.32.5+18.04
(Reading database ... 28538 files and directories currently installed.)
Preparing to unpack .../snapd_2.32.5+18.04_amd64.deb ...
Unpacking snapd (2.32.5+18.04) over (2.34.2+18.04) ...
Setting up snapd (2.32.5+18.04) ...
Installing new version of config file /etc/apparmor.d/usr.lib.snapd.snap-confine.real ...
Installing new version of config file /etc/profile.d/apps-bin-path.sh ...
snapd.snap-repair.service is a disabled or a static unit, not starting it.
Processing triggers for man-db (2.8.3-2ubuntu0.1) ...
root@uu-shutdown-test:~# unattended-upgrade --download-only
root@uu-shutdown-test:~# dbus-send --system --print-reply --dest=org.freedesktop.login1 /org/freedesktop/login1 "org.freedesktop.login1.Manager.Reboot" boolean:false
method return time=1543421249.487619 sender=:1.4 -> destination=:1.10 serial=18 reply_serial=2
root@uu-shutdown-test:~# tail -f /var/log/unattended-upgrades/unattended-upgrades-dpkg.log
Log started: 2018-11-28 16:07:34
(Reading database ... 28535 files and directories currently installed.)
Preparing to unpack .../git_1%3a2.17.1-1ubuntu0.4_amd64.deb ...
Unpacking git (1:2.17.1-1ubuntu0.4) over (1:2.17.1-1ubuntu0.3) ...
Setting up git (1:2.17.1-1ubuntu0.4) ...
Log ended: 2018-11-28 16:07:39

Log started: 2018-11-28 16:07:40
(Reading database ... 28535 files and directories currently installed.)
Preparing to unpack .../git-man_1%3a2.17.1-1ubuntu0.4_all.deb ...
Unpacking git-man (1:2.17.1-1ubuntu0.4) over (1:2.17.1-1ubuntu0.3) ...
Setting up git-man (1:2.17.1-1ubuntu0.4) ...
Processing triggers for man-db (2.8.3-2ubuntu0.1) ...
Log ended: 2018-11-28 16:07:43

Log started: 2018-11-28 16:07:43
(Reading database ... 28535 files and directories currently installed.)
Preparing to unpack .../snapd_2.34.2+18.04_amd64.deb ...
Unpacking snapd (2.34.2+18.04) over (2.32.5+18.04) ...
Setting up snapd (2.34.2+18.04) ...
Installing new version of config file /etc/apparmor.d/usr.lib.snapd.snap-confine.real ...
Installing new version of config file /etc/profile.d/apps-bin-path.sh ...
snapd.snap-repair.service is a disabled or a static unit, not starting it.
Processing triggers for man-db (2.8.3-2ubuntu0.1) ...
Log ended: 2018-11-28 16:07:48

Log started: 2018-11-28 16:07:49
(Reading database ... 28538 files and directories currently installed.)
Preparing to unpack .../sosreport_3.6-1ubuntu0.18.04.2_amd64.deb ...
Unpacking sosreport (3.6-1ubuntu0.18.04.2) over (3.5-1ubuntu3.18.04.1) ...
Setting up sosreport (3.6-1ubuntu0.18.04.2) ...
Processing triggers for man-db (2.8.3-2ubuntu0.1) ...
Log ended: 2018-11-28 16:07:53