Останавливаем автоматическое обновление на Ubuntu Server 20.04

$ systemctl list-timers | grep apt
Fri 2021-05-07 13:16:23 UTC 45min left     Fri 2021-05-07 03:14:33 UTC 9h ago      apt-daily.timer              apt-daily.service
Sat 2021-05-08 06:03:37 UTC 17h left       Fri 2021-05-07 06:12:24 UTC 6h ago      apt-daily-upgrade.timer      apt-daily-upgrade.service

systemctl stop apt-daily.timer
systemctl disable apt-daily.timer
systemctl mask apt-daily.service
 
systemctl stop apt-daily-upgrade.timer
systemctl disable apt-daily-upgrade.timer
systemctl mask apt-daily-upgrade.service

### automatic installation of security upgrades
apt-get autoremove --purge unattended-upgrades