Disclaimer, I have very little experience with Docker and servers in general. Most of the server-related things I do by following manuals created by former employees and a lot of Googling.

We are using Docker swarm to manage updates to our Docker containers. We also use unattended upgrades for security upgrades.
After unattended upgrades runs, all containers are created and all Docker services are running normally (e.g. someappservice_cache or someappservice_someappservice), except a Cron instance running in a separate Docker service (someappservice_cron).
Whenever I need to update a Docker service manually this problem doesn't occur. So after every unattended upgrades run I need to manually restart the Cron services to get the Cron service back to running normally. These are the commands I use to manually restart the service:

git checkout newappversion
sudo docker-compose build
sudo docker-compose config > someappservice.docker.stack
sudo docker stack deploy --compose-file someappservice.docker.stack someappservice
sudo docker service update --force someappservice_cron

I'm not sure why it doesn't work after unattended upgrades has done it's thing. Does anyone have a clue what could be going wrong?

This is the cron.Dockerfile:

FROM alpine:latest

RUN apk add --update apk-cron curl tzdata

COPY docker-entrypoint.sh /
COPY crontab.txt timeout-check.sh notifications-email-daily.sh notifications-email-hourly.sh /

RUN /usr/bin/crontab /crontab.txt

CMD [ "/docker-entrypoint.sh" ]

This is the docker-entrypoint.sh:


# start cron
/usr/sbin/crond -f -l 8

This is the 50unattended-upgrades file:

// 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 {
    // 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.
//  "${distro_id}:${distro_codename}-updates";
//  "${distro_id}:${distro_codename}-proposed";
//  "${distro_id}:${distro_codename}-backports";

// Python regular expressions, matching packages to exclude from upgrading
Unattended-Upgrade::Package-Blacklist {
    // The following matches all packages starting with linux-
//  "linux-";

    // Use $ to explicitely define the end of a package name. Without
    // the $, "libc6" would match all of them.
//  "libc6$";
//  "libc6-dev$";
//  "libc6-i686$";

    // Special characters need escaping
//  "libstdc\+\+6$";

    // The following matches packages like xen-system-amd64, xen-utils-4.1,
    // xenstore-utils and libxenstore3.0
//  "(lib)?xen(store)?";

    // For more information about Python regular expressions, see
    // https://docs.python.org/3/howto/regex.html

// This option controls whether the development release of Ubuntu will be
// upgraded automatically. Valid values are "true", "false", and "auto".
Unattended-Upgrade::DevRelease "auto";

// 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 "true";

// 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 "true";

// Install all updates 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-upgrades increases logind's InhibitDelayMaxSec to 30s.
// This allows more time for unattended-upgrades to shut down gracefully
// or even install a few packages in InstallOnShutdown mode, but is still a
// big step back from the 30 minutes allowed for InstallOnShutdown previously.
// Users enabling InstallOnShutdown mode are advised to increase
// InhibitDelayMaxSec even further, possibly to 30 minutes.
//Unattended-Upgrade::InstallOnShutdown "false";

// 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. "[email protected]"
//Unattended-Upgrade::Mail "";

// Set this value to one of:
//    "always", "only-on-error" or "on-change"
// If this is not set, then any legacy MailOnlyOnError (boolean) value
// is used to chose between "only-on-error" and "on-change"
//Unattended-Upgrade::MailReport "on-change";

// 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 newly unused dependencies after the upgrade
//Unattended-Upgrade::Remove-New-Unused-Dependencies "true";

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

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

// Automatically reboot even if there are users currently logged in
// when Unattended-Upgrade::Automatic-Reboot is set to true
//Unattended-Upgrade::Automatic-Reboot-WithUsers "true";

// If automatic reboot is enabled and needed, reboot at the specific
// time instead of immediately
//  Default: "now"
Unattended-Upgrade::Automatic-Reboot-Time "23:10";

// 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";

// Verbose logging
// Unattended-Upgrade::Verbose "false";

// Print debugging information both in unattended-upgrades and
// in unattended-upgrade-shutdown
// Unattended-Upgrade::Debug "false";

// Allow package downgrade if Pin-Priority exceeds 1000
// Unattended-Upgrade::Allow-downgrade "false";

This is part of the docker-compose.yml:

      context: cron
      dockerfile: cron.Dockerfile
    image: cron:latest
      - someappservice
      - someappservice
      replicas: 1
  • 1
    What is the restart policy of the container? Please show you docker-compose.yml Jun 16, 2022 at 12:18
  • @GeraldSchneider I've added it at the bottom
    – Jan-Pieter
    Jun 16, 2022 at 12:22

1 Answer 1


You don't have any restart policy configured. The default restart policy is:

No: Do not automatically restart the container.

Add the restart policy to your compose file.

    # your definition
    restart: unless-stopped
  • None of the Docker services in the Docker stacks has a restart policy defined and the other services restart properly (e.g. codeshare.io/wn8Mqp). Is this something specifically needed for Cron containers?
    – Jan-Pieter
    Jun 16, 2022 at 12:38

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