unattended-upgradedes не загружает обновления, если я не запустил apt-get update

unattended-updates не обновляет список пакетов, если я не запустил apt-get update вручную. Как я могу заставить его обновлять список пакетов, чтобы он выполнял обновления без присмотра? Я запускаю VPS-сервер с Ubuntu 18.04, используя образ Wordpress от Vultr.

Содержание /var/log/unattended-upgrades/unattended-upgrades.log :

2021-05-01 06:41:22,558 INFO Initial blacklisted packages:
2021-05-01 06:41:22,559 INFO Initial whitelisted packages:
2021-05-01 06:41:22,559 INFO Starting unattended upgrades script
2021-05-01 06:41:22,559 INFO Allowed origins are: o=Ubuntu,a=bionic, o=Ubuntu,a=bionic-security, o=UbuntuESMApps,a=bionic-apps-security, o=UbuntuESM,a=bionic-infra-security, o=Ubuntu,a=bionic-updates
2021-05-01 06:41:25,040 INFO No packages found that can be upgraded unattended and no pending auto-removals
2021-05-02 06:07:22,666 INFO Initial blacklisted packages:
2021-05-02 06:07:22,667 INFO Initial whitelisted packages:
2021-05-02 06:07:22,667 INFO Starting unattended upgrades script
2021-05-02 06:07:22,667 INFO Allowed origins are: o=Ubuntu,a=bionic, o=Ubuntu,a=bionic-security, o=UbuntuESMApps,a=bionic-apps-security, o=UbuntuESM,a=bionic-infra-security, o=Ubuntu,a=bionic-updates
2021-05-02 06:07:25,055 INFO No packages found that can be upgraded unattended and no pending auto-removals
2021-05-03 06:46:12,366 INFO Initial blacklisted packages:
2021-05-03 06:46:12,369 INFO Initial whitelisted packages:
2021-05-03 06:46:12,369 INFO Starting unattended upgrades script
2021-05-03 06:46:12,369 INFO Allowed origins are: o=Ubuntu,a=bionic, o=Ubuntu,a=bionic-security, o=UbuntuESMApps,a=bionic-apps-security, o=UbuntuESM,a=bionic-infra-security, o=Ubuntu,a=bionic-updates
2021-05-03 06:46:15,002 INFO No packages found that can be upgraded unattended and no pending auto-removals

Содержание /etc/apt/apt.conf.d/20auto-upgrades :

APT::Periodic::Update-Package-Lists "1";
APT::Periodic::Unattended-Upgrade "1";
APT::Periodic::Download-Upgradeable-Packages "1";
APT::Periodic::AutocleanInterval "7";

Содержимое /etc/apt/apt.conf.d/50unattended-upgrades :

// Automatically upgrade packages from these (origin:archive) pairs
//
// Note that in Ubuntu security updates may pull in new dependencies
// from non-security sources (e.g. chromium). By allowing the release
// pocket these get automatically pulled in.
Unattended-Upgrade::Allowed-Origins {
        "${distro_id}:${distro_codename}";
        "${distro_id}:${distro_codename}-security";
        // Extended Security Maintenance; doesn't necessarily exist for
        // every release and this system may not have it installed, but if
        // available, the policy for updates is such that unattended-upgrades
        // should also install from here by default.
        "${distro_id}ESMApps:${distro_codename}-apps-security";
        "${distro_id}ESM:${distro_codename}-infra-security";
        "${distro_id}:${distro_codename}-updates";
//      "${distro_id}:${distro_codename}-proposed";
//      "${distro_id}:${distro_codename}-backports";
};

// List of packages to not update (regexp are supported)
Unattended-Upgrade::Package-Blacklist {
//      "vim";
//      "libc6";
//      "libc6-dev";
//      "libc6-i686";
};

// This option will controls whether the development release of Ubuntu will be
// upgraded automatically.
Unattended-Upgrade::DevRelease "false";

// This option allows you to control if on a unclean dpkg exit
// unattended-upgrades will automatically run
//   dpkg --force-confold --configure -a
// The default is true, to ensure updates keep getting installed
//Unattended-Upgrade::AutoFixInterruptedDpkg "false";

// Split the upgrade into the smallest possible chunks so that
// they can be interrupted with SIGTERM. This makes the upgrade
// a bit slower but it has the benefit that shutdown while a upgrade
// is running is possible (with a small delay)
//Unattended-Upgrade::MinimalSteps "false";

// Install all unattended-upgrades when the machine is shutting down
// instead of doing it in the background while the machine is running
// This will (obviously) make shutdown slower
//Unattended-Upgrade::InstallOnShutdown "true";

// Send email to this address for problems or packages upgrades
// If empty or unset then no email is sent, make sure that you
// have a working mail setup on your system. A package that provides
// 'mailx' must be installed. E.g. "user@example.com"
//Unattended-Upgrade::Mail "root";

// Set this value to "true" to get emails only on errors. Default
// is to always send a mail if Unattended-Upgrade::Mail is set
//Unattended-Upgrade::MailOnlyOnError "true";

// Remove unused automatically installed kernel-related packages
// (kernel images, kernel headers and kernel version locked tools).
Unattended-Upgrade::Remove-Unused-Kernel-Packages "true";

// Do automatic removal of new unused dependencies after the upgrade
// (equivalent to apt-get autoremove)
Unattended-Upgrade::Remove-Unused-Dependencies "true";

// Automatically reboot *WITHOUT CONFIRMATION*
//  if the file /var/run/reboot-required is found after the upgrade
Unattended-Upgrade::Automatic-Reboot "true";

// If automatic reboot is enabled and needed, reboot at the specific
// time instead of immediately
//  Default: "now"
//Unattended-Upgrade::Automatic-Reboot-Time "02:00";

// Use apt bandwidth limit feature, this example limits the download
// speed to 70kb/sec
//Acquire::http::Dl-Limit "70";

// Enable logging to syslog. Default is False
// Unattended-Upgrade::SyslogEnable "false";

// Specify syslog facility. Default is daemon
// Unattended-Upgrade::SyslogFacility "daemon";

// Download and install upgrades only on AC power
// (i.e. skip or gracefully stop updates on battery)
// Unattended-Upgrade::OnlyOnACPower "true";

// Download and install upgrades only on non-metered connection
// (i.e. skip or gracefully stop updates on a metered connection)
// Unattended-Upgrade::Skip-Updates-On-Metered-Connections "true";

Выполняется unattended-updates -v -d --dry-run без предварительного запуска apt-get update :

Initial blacklisted packages:
Initial whitelisted packages:
Starting unattended upgrades script
Allowed origins are: o=Ubuntu,a=bionic, o=Ubuntu,a=bionic-security, o=UbuntuESMApps,a=bionic-apps-security, o=UbuntuESM,a=bionic-infra-security, o=Ubuntu,a=bionic-updates
Using (^linux-image-[0-9]+\.[0-9\.]+-.*|^linux-headers-[0-9]+\.[0-9\.]+-.*|^linux-image-extra-[0-9]+\.[0-9\.]+-.*|^linux-modules-[0-9]+\.[0-9\.]+-.*|^linux-modules-extra-[0-9]+\.[0-9\.]+-.*|^linux-signed-image-[0-9]+\.[0-9\.]+-.*|^linux-image-unsigned-[0-9]+\.[0-9\.]+-.*|^kfreebsd-image-[0-9]+\.[0-9\.]+-.*|^kfreebsd-headers-[0-9]+\.[0-9\.]+-.*|^gnumach-image-[0-9]+\.[0-9\.]+-.*|^.*-modules-[0-9]+\.[0-9\.]+-.*|^.*-kernel-[0-9]+\.[0-9\.]+-.*|^linux-backports-modules-.*-[0-9]+\.[0-9\.]+-.*|^linux-modules-.*-[0-9]+\.[0-9\.]+-.*|^linux-tools-[0-9]+\.[0-9\.]+-.*|^linux-cloud-tools-[0-9]+\.[0-9\.]+-.*|^linux-buildinfo-[0-9]+\.[0-9\.]+-.*|^linux-source-[0-9]+\.[0-9\.]+-.*|^linux-image-[0-9]+\.[0-9\.]+-.*|^linux-headers-[0-9]+\.[0-9\.]+-.*|^linux-image-extra-[0-9]+\.[0-9\.]+-.*|^linux-modules-[0-9]+\.[0-9\.]+-.*|^linux-modules-extra-[0-9]+\.[0-9\.]+-.*|^linux-signed-image-[0-9]+\.[0-9\.]+-.*|^linux-image-unsigned-[0-9]+\.[0-9\.]+-.*|^kfreebsd-image-[0-9]+\.[0-9\.]+-.*|^kfreebsd-headers-[0-9]+\.[0-9\.]+-.*|^gnumach-image-[0-9]+\.[0-9\.]+-.*|^.*-modules-[0-9]+\.[0-9\.]+-.*|^.*-kernel-[0-9]+\.[0-9\.]+-.*|^linux-backports-modules-.*-[0-9]+\.[0-9\.]+-.*|^linux-modules-.*-[0-9]+\.[0-9\.]+-.*|^linux-tools-[0-9]+\.[0-9\.]+-.*|^linux-cloud-tools-[0-9]+\.[0-9\.]+-.*|^linux-buildinfo-[0-9]+\.[0-9\.]+-.*|^linux-source-[0-9]+\.[0-9\.]+-.*) regexp to find kernel packages
Using (^linux-image-4\.15\.0\-142\-generic$|^linux-headers-4\.15\.0\-142\-generic$|^linux-image-extra-4\.15\.0\-142\-generic$|^linux-modules-4\.15\.0\-142\-generic$|^linux-modules-extra-4\.15\.0\-142\-generic$|^linux-signed-image-4\.15\.0\-142\-generic$|^linux-image-unsigned-4\.15\.0\-142\-generic$|^kfreebsd-image-4\.15\.0\-142\-generic$|^kfreebsd-headers-4\.15\.0\-142\-generic$|^gnumach-image-4\.15\.0\-142\-generic$|^.*-modules-4\.15\.0\-142\-generic$|^.*-kernel-4\.15\.0\-142\-generic$|^linux-backports-modules-.*-4\.15\.0\-142\-generic$|^linux-modules-.*-4\.15\.0\-142\-generic$|^linux-tools-4\.15\.0\-142\-generic$|^linux-cloud-tools-4\.15\.0\-142\-generic$|^linux-buildinfo-4\.15\.0\-142\-generic$|^linux-source-4\.15\.0\-142\-generic$|^linux-image-4\.15\.0\-142\-generic$|^linux-headers-4\.15\.0\-142\-generic$|^linux-image-extra-4\.15\.0\-142\-generic$|^linux-modules-4\.15\.0\-142\-generic$|^linux-modules-extra-4\.15\.0\-142\-generic$|^linux-signed-image-4\.15\.0\-142\-generic$|^linux-image-unsigned-4\.15\.0\-142\-generic$|^kfreebsd-image-4\.15\.0\-142\-generic$|^kfreebsd-headers-4\.15\.0\-142\-generic$|^gnumach-image-4\.15\.0\-142\-generic$|^.*-modules-4\.15\.0\-142\-generic$|^.*-kernel-4\.15\.0\-142\-generic$|^linux-backports-modules-.*-4\.15\.0\-142\-generic$|^linux-modules-.*-4\.15\.0\-142\-generic$|^linux-tools-4\.15\.0\-142\-generic$|^linux-cloud-tools-4\.15\.0\-142\-generic$|^linux-buildinfo-4\.15\.0\-142\-generic$|^linux-source-4\.15\.0\-142\-generic$) regexp to find running kernel packages
pkgs that look like they should be upgraded:
Fetched 0 B in 0s (0 B/s)
fetch.run() result: 0
blacklist: []
whitelist: []
No packages found that can be upgraded unattended and no pending auto-removals