How to use this image

All examples in this guide use the public image. If you've mirrored the repository for your own use (for example, to your Docker Hub namespace), update your commands to reference the mirrored image instead of the public one.

For example:

• Public image: dhi.io/<repository>:<tag>
• Mirrored image: <your-namespace>/dhi-<repository>:<tag>

For the examples, you must first use docker login dhi.io to authenticate to the registry to pull the images.

Start an Unleash instance

Unleash requires a PostgreSQL database. First, create a Docker network and start a PostgreSQL container:

docker network create unleash-net
docker run -d --name postgres --network unleash-net \
    -e POSTGRES_DB=unleash \
    -e POSTGRES_USER=unleash \
    -e POSTGRES_PASSWORD=changeme \
    postgres:16

Then start Unleash:

docker run -d --name unleash \
    --network unleash-net \
    -p 4242:4242 \
    -e DATABASE_URL="postgres://unleash:changeme@postgres:5432/unleash?sslmode=disable" \
    dhi.io/unleash:<tag>

Navigate to http://localhost:4242 in your browser. The default admin credentials are admin / unleash4all.

Configuration

Unleash is configured through environment variables. For a complete list, see the Unleash configuration documentation⁠.

Unleash attempts SSL connections to PostgreSQL by default. When connecting to PostgreSQL without SSL, append ?sslmode=disable to the DATABASE_URL connection string.

Docker Compose example

services:
  postgres:
    image: postgres:16
    environment:
      POSTGRES_DB: unleash
      POSTGRES_USER: unleash
      POSTGRES_PASSWORD: changeme
    volumes:
      - postgres-data:/var/lib/postgresql/data
  unleash:
    image: dhi.io/unleash:<tag>
    ports:
      - "4242:4242"
    environment:
      DATABASE_URL: "postgres://unleash:changeme@postgres:5432/unleash?sslmode=disable"
    depends_on:
      - postgres
volumes:
  postgres-data:

Differences from upstream

The Docker Hardened Image differs from the upstream unleashorg/unleash-server image in the following ways:

Migrate to a Docker Hardened Image

To migrate your application to a Docker Hardened Image, you must update your Dockerfile. At minimum, you must update the base image in your existing Dockerfile to a Docker Hardened Image. This and a few other common changes are listed in the following table of migration notes.

The following steps outline the general migration process.

1. Find hardened images for your app.

   A hardened image may have several variants. Inspect the image tags and find the image variant that meets your needs.

2. Update the base image in your Dockerfile.

   Update the base image in your application's Dockerfile to the hardened image you found in the previous step. For framework images, this is typically going to be an image tagged as dev because it has the tools needed to install packages and dependencies.

3. For multi-stage Dockerfiles, update the runtime image in your Dockerfile.

   To ensure that your final image is as minimal as possible, you should use a multi-stage build. All stages in your Dockerfile should use a hardened image. While intermediary stages will typically use images tagged as dev, your final runtime stage should use a non-dev image variant.

4. Install additional packages

   Docker Hardened Images contain minimal packages in order to reduce the potential attack surface. You may need to install additional packages in your Dockerfile. To view if a package manager is available for an image variant, select the Tags tab for this repository. To view what packages are already installed in an image variant, select the Tags tab for this repository, and then select a tag.

Image variants

Docker Hardened Images come in different variants depending on their intended use.

• Runtime variants are designed to run your application in production. These images are intended to be used either directly or as the FROM image in the final stage of a multi-stage build. These images typically:

  • Run as the nonroot user
  • Do not include a shell or a package manager
  • Contain only the minimal set of libraries needed to run the app

• Build-time variants typically include dev in the variant name and are intended for use in the first stage of a multi-stage Dockerfile. These images typically:

  • Run as the root user
  • Include a shell and package manager
  • Are used to build or compile applications

• FIPS variants include fips in the variant name and tag. They come in both runtime and build-time variants. These variants use cryptographic modules that have been validated under FIPS 140, a U.S. government standard for secure cryptographic operations. For example, usage of MD5 fails in FIPS variants.

Troubleshooting

General debugging

The hardened images intended for runtime don't contain a shell nor any tools for debugging. The recommended method for debugging applications built with Docker Hardened Images is to use Docker Debug⁠ to attach to these containers. Docker Debug provides a shell, common debugging tools, and lets you install other tools in an ephemeral, writable layer that only exists during the debugging session.

Privileged ports

Non-dev hardened images run as a nonroot user by default. As a result, applications in these images can't bind to privileged ports (below 1024) when running in Kubernetes or in Docker Engine versions older than 20.10. To avoid issues, configure your application to listen on port 1025 or higher inside the container, even if you map it to a lower port on the host. For example, docker run -p 80:8080 my-image will work because the port inside the container is 8080, and docker run -p 80:81 my-image won't work because the port inside the container is 81.

No shell

By default, image variants intended for runtime don't contain a shell. Use dev images in build stages to run shell commands and then copy any necessary artifacts into the runtime stage. In addition, use Docker Debug to debug containers with no shell.

Entry point

The upstream image inherits the Node image's docker-entrypoint.sh wrapper, which prepends node for Node.js flags and scripts before executing the command. The Docker Hardened Image runs node directly with /opt/unleash/dist/server.js as the default command. Default startup and Node.js flags such as --version work the same way, but shell-style command overrides aren't supported by the runtime variant because it doesn't include a shell. Use Docker Debug or a dev variant for interactive shell-based debugging.

Database connection

Unleash must be able to reach a PostgreSQL server. Ensure the DATABASE_URL environment variable is set correctly and that both containers are on the same Docker network. If using Docker Compose, the depends_on directive ensures PostgreSQL starts before Unleash.

Database migrations

Unleash automatically runs database migrations on startup. If you see migration errors, ensure the database user has sufficient privileges to create tables and run migrations.