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How we automate container updates on mittwald

We run several containers on mittwald - mainly Solr and n8n instances for various projects.

Container images get regular updates with new features and security patches. Clicking 'update' in the mittwald interface works fine for one or two containers, but becomes tedious when you're managing multiple projects.

Since we use :latest tags deliberately, we built a simple cron solution to handle updates automatically.

Show larger version for: Diese Grafik zeigt, wie ein Projekt angelegt wird.
Show larger version for: The image shows a section for installing software: "Node.js version 24.7.0 is available for installation. One software listing displayed."
Show larger version for: German interface for creating a new API token. Fields include a name box labeled 'mw-cli-cron-write', an optional checkbox to set an expiration date, and permissions section to enable 'Schreibzugrif‌ automó nucleotidesen’ access. Two clickable buttons at the bottom: 'Abbrechen' and 'Anlegen'.

Setup requirements

You'll need a dedicated project to run the cron job:

  • Create a static site project (we only use it as execution environment)
  • Add Node.js via software management
  • SSH access to the project
  • Install the mittwald CLI: npm install -g @mittwald/cli
  • Generate an API token with write permissions:
  • Authenticate with your token: mw login token
Show larger version for: A project details section showing a short project ID
Show larger version for: This image shows a running Docker container status display. Described alternative text:interface indicating a currently active (running) container with hostname, blurred Short-ID, Stack-ID, and its last activity timestamp

Finding your project and container IDs

Each container update requires both project-id and container-id. Get them via CLI or mittwald's interface.

List all projects:

mw project list

Show containers for a specific project:

mw container ls --project-id <project-id>

Alternatively, grab the IDs from the mittwald dashboard - they're visible in the URL or container details.

The update command

Updating a container is straightforward:

mw container recreate <container-id> --pull --project-id <project-id>

The --pull flag ensures you get the latest image

recreate gives you a clean container restart

Show larger version for: This image displays a cron job configuration for a script named "update-container.sh" in the "docker-updater" app.

Automating with cron

We wrap the command in a simple bash script:

#!/bin/sh
exec /files/.mwsoftware/node/bin/mw container recreate $1 --pull --project-id $2

Now we can call this script from cron with different container and project IDs. Makes it easy to update multiple containers across different projects automatically.

A word of caution

Using :latest tags is convenient but requires some thought. If you're running databases or services with strict version dependencies, automatic updates might break things.
Also consider when to run updates - we usually schedule them during low-traffic hours.
This approach works well for our internal tools where brief downtime isn't critical.

For non-mittwald setups

When we're running containers elsewhere, we use WUD (What's up Docker) for monitoring and updates.

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