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 a WireMock image

Run the following command to start WireMock with default settings:

$ docker run -d --name wiremock -p 8080:8080 dhi.io/wiremock:<tag>

WireMock will start on port 8080. WireMock doesn't serve content at the root path / by default. To verify WireMock is running, access the admin API at http://localhost:8080/__admin/mappings or the Swagger UI at http://localhost:8080/__admin/swagger-ui/.

Environment variables

WireMock supports configuration through environment variables:

Customizing Java options

Since the runtime image does not include a shell, JAVA_OPTS environment variables are not automatically processed. To pass JVM options, override the command:

$ docker run -d --name wiremock \
  -p 8080:8080 \
  dhi.io/wiremock:<tag> \
  -Xmx512m -Xms256m -jar /usr/local/bin/wiremock-standalone.jar

Customizing WireMock options

Since the runtime image does not include a shell, WIREMOCK_OPTIONS environment variables are not automatically processed. To pass WireMock-specific options, override the command:

$ docker run -d --name wiremock \
  -p 8080:8080 \
  dhi.io/wiremock:<tag> \
  -jar /usr/local/bin/wiremock-standalone.jar --port 8080 --verbose

Combining Java and WireMock options

To pass both JVM options and WireMock options, override the command with all arguments:

$ docker run -d --name wiremock \
  -p 8080:8080 \
  dhi.io/wiremock:<tag> \
  -Xmx512m -Xms256m -jar /usr/local/bin/wiremock-standalone.jar --port 8080 --verbose

Health checks

WireMock provides a health endpoint at /__admin/health that can be used for container health checks.

Docker Compose

Since Docker Hardened Images don't include curl in runtime variants, Docker Compose health checks that require curl are not supported. Instead, use one of these approaches:

Option 1: Use a sidecar container with busybox for monitoring:

services:
  wiremock:
    image: dhi.io/wiremock:<tag>
    ports:
      - "8080:8080"

  # Sidecar container for health monitoring
  wiremock-healthcheck:
    image: dhi.io/busybox:1
    depends_on:
      - wiremock
    command: ["sh", "-c", "while true; do wget -q -O- http://wiremock:8080/__admin/health || exit 1; sleep 30; done"]
    restart: unless-stopped

Option 2: Use external monitoring tools that can perform HTTP health checks without requiring curl inside the container.

Kubernetes

Use HTTP probes for liveness and readiness checks:

apiVersion: v1
kind: Pod
metadata:
  name: wiremock
spec:
  containers:
    - name: wiremock
      image: dhi.io/wiremock:<tag>
      ports:
        - containerPort: 8080
      livenessProbe:
        httpGet:
          path: /__admin/health
          port: 8080
        initialDelaySeconds: 30
        periodSeconds: 10
        timeoutSeconds: 5
        failureThreshold: 3
      readinessProbe:
        httpGet:
          path: /__admin/health
          port: 8080
        initialDelaySeconds: 10
        periodSeconds: 5
        timeoutSeconds: 3
        failureThreshold: 3

Common WireMock use cases

Basic API mocking

Start WireMock and create a stub mapping:

# Start WireMock
$ docker run -d --name wiremock -p 8080:8080 dhi.io/wiremock:<tag>

# Create a stub mapping
$ curl -X POST http://localhost:8080/__admin/mappings \
  -H "Content-Type: application/json" \
  -d '{
    "request": {
      "method": "GET",
      "url": "/api/test"
    },
    "response": {
      "status": 200,
      "body": "Hello from WireMock"
    }
  }'

# Test the stub
$ curl http://localhost:8080/api/test

WireMock with persistence

WireMock stores stub mappings and files in /home/wiremock. Mount this directory to persist data:

$ docker run -d --name wiremock \
  -p 8080:8080 \
  -v wiremock-data:/home/wiremock \
  dhi.io/wiremock:<tag>

The directory structure:

• /home/wiremock/mappings/ - Stub mappings (JSON files)
• /home/wiremock/__files/ - Response body files

Recording from a real API

Use WireMock's record mode to capture requests and responses:

$ docker run -d --name wiremock \
  -p 8080:8080 \
  dhi.io/wiremock:<tag> \
  -jar /usr/local/bin/wiremock-standalone.jar --proxy-all=https://api.example.com --record-mappings

Using pre-configured mappings

Mount a directory with your stub mappings:

$ docker run -d --name wiremock \
  -p 8080:8080 \
  -v $(pwd)/mappings:/home/wiremock/mappings \
  dhi.io/wiremock:<tag>

Image variants

Docker Hardened Images come in different variants depending on their intended use. Image variants are identified by their tag.

• 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 a 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 tag 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

To view the image variants and get more information about them, select the Tags tab for this repository, and then select a tag.

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. Inspect the image variants to identify which packages are already installed.

   Only images tagged as dev typically have package managers. You should use a multi-stage Dockerfile to install the packages. Install the packages in the build stage that uses a dev image. Then, if needed, copy any necessary artifacts to the runtime stage that uses a non-dev image.

   For Alpine-based images, you can use apk to install packages. For Debian-based images, you can use apt-get to install packages.

Troubleshooting migration

The following are common issues that you may encounter during migration.

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.

Permissions

By default image variants intended for runtime, run as the nonroot user. Ensure that necessary files and directories are accessible to the nonroot user. You may need to copy files to different directories or change permissions so your application running as the nonroot user can access them.

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

Docker Hardened Images may have different entry points than images such as Docker Official Images. Use docker inspect to inspect entry points for Docker Hardened Images and update your Dockerfile if necessary.

The DHI WireMock image runs java directly with -jar /usr/local/bin/wiremock-standalone.jar, rather than using a shell script like the upstream image. This means:

• Standard usage works identically to upstream
• WireMock functionality is unchanged
• JAVA_OPTS and WIREMOCK_OPTIONS environment variables have no effect (see the note in Environment variables⁠)
• The upstream uid environment variable feature (for user switching via gosu) is not available in DHI images. DHI images run as nonroot user by default, so this feature is typically unnecessary.