Deploy unattended-upgrades (described in https://help.ubuntu.com/community/AutomaticSecurityUpdates#Using_the_.22unattended-upgrades.22_package)

deploy_unattended-upgrades.sh

# wget https://gist.github.com/ydf/8c5a7f80ee84dd24c5c676f84929b1f8/raw/dda2ab31a16fc5ab436666d2162bd2db85350632/deploy_unattended-upgrades.sh -O /tmp/a && sh /tmp/a
apt-get -y install unattended-upgrades && \
cat > /etc/apt/apt.conf.d/10periodic <<EOF
APT::Periodic::Update-Package-Lists "1";
APT::Periodic::Download-Upgradeable-Packages "1";
APT::Periodic::AutocleanInterval "3";
APT::Periodic::Unattended-Upgrade "1";
EOF

sed -i 's#//\t"${distro_id}:${distro_codename}-updates"#\t"${distro_id}:${distro_codename}-updates"#' /etc/apt/apt.conf.d/50unattended-upgrades && \
sed -i 's#//Unattended-Upgrade::Remove-Unused-Dependencies "false"#Unattended-Upgrade::Remove-Unused-Dependencies "true"#' /etc/apt/apt.conf.d/50unattended-upgrades && \
sed -i 's#//Unattended-Upgrade::Automatic-Reboot "false"#Unattended-Upgrade::Automatic-Reboot "true"#' /etc/apt/apt.conf.d/50unattended-upgrades && \
sed -i 's#//Unattended-Upgrade::Automatic-Reboot-Time "02:00"#Unattended-Upgrade::Automatic-Reboot-Time "04:00"#' /etc/apt/apt.conf.d/50unattended-upgrades