Comment 9 for bug 1789637

Tested 1.1ubuntu1.18.04.7~16.04.1:

Previous version:

root@x-uu-1789637-2:~# strace unattended-upgrade --verbose --dry-run 2>&1 | grep lock
open("/var/lib/dpkg/lock-frontend", O_RDWR|O_CREAT|O_NOFOLLOW, 0640) = 4
open("/var/lib/dpkg/lock", O_RDWR|O_CREAT|O_NOFOLLOW, 0640) = 5
open("/var/run/unattended-upgrades.lock", O_RDWR|O_CREAT|O_NOFOLLOW, 0640) = 45
open("/var/cache/apt/archives/lock", O_RDWR|O_CREAT|O_NOFOLLOW, 0640) = 4

Previous version with python3-apt supporting frontend lock:

root@x-uu-1789637-2:~# apt install -qq python3-apt
The following package was automatically installed and is no longer required:
  libfreetype6
Use 'apt autoremove' to remove it.
Suggested packages:
  python3-apt-dbg python-apt-doc
The following packages will be upgraded:
  python3-apt
1 upgraded, 0 newly installed, 0 to remove and 13 not upgraded.
Need to get 138 kB of archives.
After this operation, 6,144 B of additional disk space will be used.
(Reading database ... 25712 files and directories currently installed.)
Preparing to unpack .../python3-apt_1.1.0~beta1ubuntu0.16.04.3_amd64.deb ...
Unpacking python3-apt (1.1.0~beta1ubuntu0.16.04.3) over (1.1.0~beta1ubuntu0.16.04.2) ...
Setting up python3-apt (1.1.0~beta1ubuntu0.16.04.3) ...
root@x-uu-1789637-2:~# strace unattended-upgrade --verbose --dry-run 2>&1 | grep lock
open("/var/lib/dpkg/lock-frontend", O_RDWR|O_CREAT|O_NOFOLLOW, 0640) = 4
open("/var/lib/dpkg/lock", O_RDWR|O_CREAT|O_NOFOLLOW, 0640) = 5
open("/var/run/unattended-upgrades.lock", O_RDWR|O_CREAT|O_NOFOLLOW, 0640) = 45
open("/var/lib/dpkg/lock-frontend", O_RDWR|O_CREAT|O_NOFOLLOW, 0640) = 4
open("/var/lib/dpkg/lock", O_RDWR|O_CREAT|O_NOFOLLOW, 0640) = 5
open("/var/cache/apt/archives/lock", O_RDWR|O_CREAT|O_NOFOLLOW, 0640) = 48
open("/var/lib/dpkg/lock", O_RDWR|O_CREAT|O_NOFOLLOW, 0640) = 5

Fixed version:

root@x-uu-1789637-2:~# apt install -qq unattended-upgrades
The following package was automatically installed and is no longer required:
  libfreetype6
Use 'apt autoremove' to remove it.
Suggested packages:
  bsd-mailx default-mta | mail-transport-agent needrestart
The following packages will be upgraded:
  unattended-upgrades
1 upgraded, 0 newly installed, 0 to remove and 12 not upgraded.
Need to get 40.2 kB of archives.
After this operation, 69.6 kB of additional disk space will be used.
Preconfiguring packages ...
(Reading database ... 25712 files and directories currently installed.)
Preparing to unpack .../unattended-upgrades_1.1ubuntu1.18.04.7~16.04.1_all.deb ...
Unpacking unattended-upgrades (1.1ubuntu1.18.04.7~16.04.1) over (0.90ubuntu0.10) ...
Processing triggers for systemd (229-4ubuntu21.15) ...
Processing triggers for ureadahead (0.100.0-19) ...
Processing triggers for man-db (2.7.5-1) ...
Setting up unattended-upgrades (:) ...
Installing new version of config file /etc/kernel/postinst.d/unattended-upgrades ...
Installing new version of config file /etc/pm/sleep.d/10_unattended-upgrades-hibernate ...
root@x-uu-1789637-2:~# strace unattended-upgrade --verbose --dry-run 2>&1 | grep lock
open("/var/run/unattended-upgrades.lock", O_RDWR|O_CREAT|O_NOFOLLOW, 0640) = 4
open("/var/lib/dpkg/lock-frontend", O_RDWR|O_CREAT|O_NOFOLLOW, 0640) = 5
open("/var/lib/dpkg/lock", O_RDWR|O_CREAT|O_NOFOLLOW, 0640) = 6
open("/var/cache/apt/archives/lock", O_RDWR|O_CREAT|O_NOFOLLOW, 0640) = 50
open("/var/lib/dpkg/lock", O_RDWR|O_CREAT|O_NOFOLLOW, 0640) = 6