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.

Run a Flyway container

Run the following docker run command to run a Flyway container.

$ docker run --rm dhi.io/flyway:11.9-jre23 info

Basic database migration

To migrate a database, you need to provide database connection details and mount your migration files:

$ docker run --rm \
  -v $(pwd)/sql:/flyway/sql \
  dhi.io/flyway:11.9-jre23 \
  -url=jdbc:postgresql://localhost:5432/mydb \
  -user=myuser \
  -password=mypassword \
  migrate

Common Flyway commands

• info: Display migration info
• migrate: Migrate the database
• clean: Drop all objects in the configured schemas
• validate: Validate applied migrations against resolved ones
• baseline: Baseline an existing database
• repair: Repair the schema history table

Environment variables

You can use environment variables to configure Flyway:

$ docker run --rm \
  -v $(pwd)/sql:/flyway/sql \
  -e FLYWAY_URL=jdbc:postgresql://localhost:5432/mydb \
  -e FLYWAY_USER=myuser \
  -e FLYWAY_PASSWORD=mypassword \
  dhi.io/flyway:11.9-jre23 \
  migrate

Configuration file

You can also mount a configuration file:

$ docker run --rm \
  -v $(pwd)/conf:/flyway/conf \
  -v $(pwd)/sql:/flyway/sql \
  dhi.io/flyway:11.9-jre23 \
  migrate

Additional examples

MySQL database migration

$ docker run --rm \
  -v $(pwd)/sql:/flyway/sql \
  -e FLYWAY_URL=jdbc:mysql://localhost:3306/mydb \
  -e FLYWAY_USER=root \
  -e FLYWAY_PASSWORD=mypassword \
  dhi.io/flyway:11.9-jre23 \
  migrate

SQL Server database migration

$ docker run --rm \
  -v $(pwd)/sql:/flyway/sql \
  -e FLYWAY_URL=jdbc:sqlserver://localhost:1433;databaseName=mydb \
  -e FLYWAY_USER=sa \
  -e FLYWAY_PASSWORD=mypassword \
  dhi.io/flyway:11.9-jre23 \
  migrate

Oracle database migration

$ docker run --rm \
  -v $(pwd)/sql:/flyway/sql \
  -e FLYWAY_URL=jdbc:oracle:thin:@localhost:1521:XE \
  -e FLYWAY_USER=system \
  -e FLYWAY_PASSWORD=mypassword \
  dhi.io/flyway:11.9-jre23 \
  migrate

Check migration status

$ docker run --rm \
  -e FLYWAY_URL=jdbc:postgresql://localhost:5432/mydb \
  -e FLYWAY_USER=myuser \
  -e FLYWAY_PASSWORD=mypassword \
  dhi.io/flyway:11.9-jre23 \
  info

Validate migrations

$ docker run --rm \
  -v $(pwd)/sql:/flyway/sql \
  -e FLYWAY_URL=jdbc:postgresql://localhost:5432/mydb \
  -e FLYWAY_USER=myuser \
  -e FLYWAY_PASSWORD=mypassword \
  dhi.io/flyway:11.9-jre23 \
  validate

Baseline existing database

$ docker run --rm \
  -e FLYWAY_URL=jdbc:postgresql://localhost:5432/mydb \
  -e FLYWAY_USER=myuser \
  -e FLYWAY_PASSWORD=mypassword \
  -e FLYWAY_BASELINE_VERSION=1.0 \
  -e FLYWAY_BASELINE_DESCRIPTION="Initial baseline" \
  dhi.io/flyway:11.9-jre23 \
  baseline

Using with Docker Compose

Create a docker-compose.yml file:

version: "3.8"
services:
  postgres:
    image: dhi.io/postgres
    environment:
      POSTGRES_DB: mydb
      POSTGRES_USER: myuser
      POSTGRES_PASSWORD: mypassword
    ports:
      - "5432:5432"
    volumes:
      - postgres_data:/var/lib/postgresql/data

  flyway:
    image: dhi.io/flyway:11.9-jre23
    command: migrate
    volumes:
      - ./sql:/flyway/sql
      - ./conf:/flyway/conf
    environment:
      FLYWAY_URL: jdbc:postgresql://postgres:5432/mydb
      FLYWAY_USER: myuser
      FLYWAY_PASSWORD: mypassword
    depends_on:
      - postgres

volumes:
  postgres_data:

Run with Docker Compose:

$ docker-compose up flyway

Advanced configuration with multiple schemas

$ docker run --rm \
  -v $(pwd)/sql:/flyway/sql \
  -e FLYWAY_URL=jdbc:postgresql://localhost:5432/mydb \
  -e FLYWAY_USER=myuser \
  -e FLYWAY_PASSWORD=mypassword \
  -e FLYWAY_SCHEMAS=public,app,audit \
  -e FLYWAY_DEFAULT_SCHEMA=app \
  dhi.io/flyway:11.9-jre23 \
  migrate

Using configuration file with custom settings

Create a flyway.conf file:

flyway.url=jdbc:postgresql://localhost:5432/mydb
flyway.user=myuser
flyway.password=mypassword
flyway.schemas=public,app
flyway.table=schema_version
flyway.locations=filesystem:/flyway/sql
flyway.validateOnMigrate=true
flyway.outOfOrder=false
flyway.baselineOnMigrate=true

Run with configuration file:

$ docker run --rm \
  -v $(pwd)/conf/flyway.conf:/flyway/conf/flyway.conf \
  -v $(pwd)/sql:/flyway/sql \
  dhi.io/flyway:11.9-jre23 \
  migrate

Repair schema history table

$ docker run --rm \
  -e FLYWAY_URL=jdbc:postgresql://localhost:5432/mydb \
  -e FLYWAY_USER=myuser \
  -e FLYWAY_PASSWORD=mypassword \
  dhi.io/flyway:11.9-jre23 \
  repair

Clean database (use with caution)

$ docker run --rm \
  -e FLYWAY_URL=jdbc:postgresql://localhost:5432/mydb \
  -e FLYWAY_USER=myuser \
  -e FLYWAY_PASSWORD=mypassword \
  -e FLYWAY_CLEAN_DISABLED=false \
  dhi.io/flyway:11.9-jre23 \
  clean

Using with secrets from files

$ docker run --rm \
  -v $(pwd)/sql:/flyway/sql \
  -v $(pwd)/secrets/db-password:/run/secrets/db-password \
  -e FLYWAY_URL=jdbc:postgresql://localhost:5432/mydb \
  -e FLYWAY_USER=myuser \
  -e FLYWAY_PASSWORD_FILE=/run/secrets/db-password \
  dhi.io/flyway:11.9-jre23 \
  migrate

Custom migration location

$ docker run --rm \
  -v $(pwd)/database/migrations:/flyway/custom-migrations \
  -e FLYWAY_URL=jdbc:postgresql://localhost:5432/mydb \
  -e FLYWAY_USER=myuser \
  -e FLYWAY_PASSWORD=mypassword \
  -e FLYWAY_LOCATIONS=filesystem:/flyway/custom-migrations \
  dhi.io/flyway:11.9-jre23 \
  migrate

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

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.

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.

Flyway-specific considerations

Migration files

Flyway looks for migration files in the /flyway/sql directory by default. When using the Docker Hardened Image, mount your migration files to this directory:

$ docker run --rm -v $(pwd)/migrations:/flyway/sql dhi.io/flyway:11.9-jre23 migrate

Configuration

Flyway configuration can be provided via:

• Command line arguments
• Environment variables (prefixed with FLYWAY_)
• Configuration files mounted to /flyway/conf

Database drivers

The Flyway image includes drivers for common databases including PostgreSQL, MySQL, Oracle, SQL Server, and others. For specialized databases, you may need to add additional JDBC drivers to your custom image.