docker - Dockerfile if else condition with external arguments

Docker - Dockerfile if else condition with external arguments

Dockerfile itself does not support if-else conditions in the way that you might expect in a programming language. However, you can achieve similar conditional behavior using multi-stage builds and build arguments.

Here's an example of how you can use build arguments to conditionally include or exclude certain steps in a Dockerfile:

# Stage 1: Build stage FROM alpine as builder ARG BUILD_TYPE WORKDIR /app COPY . . RUN if [ "$BUILD_TYPE" = "production" ]; then \ echo "Building for production" && \ # Your production build steps go here \ else \ echo "Building for development" && \ # Your development build steps go here \ fi # Stage 2: Final stage FROM alpine COPY --from=builder /app /app CMD ["echo", "Container is built"]

In this example:

  • The Dockerfile defines a build argument BUILD_TYPE.
  • In the build stage, it checks the value of BUILD_TYPE and performs different steps accordingly.
  • The final image only includes the necessary artifacts from the build stage.

You can then build your Docker image by passing the build argument:

docker build --build-arg BUILD_TYPE=production -t myimage:production .

Or for development:

docker build --build-arg BUILD_TYPE=development -t myimage:development .

Remember that multi-stage builds are available from Docker 17.05 onwards.

Note: While this approach allows for some conditional behavior, it's important to consider whether you truly need conditionals in your Dockerfile. In many cases, it might be cleaner to have separate Dockerfiles or scripts for different scenarios.

Examples

  1. "Dockerfile conditional build based on ARG value"

    # Code: ARG build_type FROM base_image AS builder RUN if [ "$build_type" = "production" ]; then \ # Production build steps \ else \ # Development build steps \ fi

    Description: This Dockerfile uses the ARG instruction to define an external argument build_type. The subsequent RUN command conditionally executes different build steps based on the value of the build_type argument.

  2. "Dockerfile conditional ARG with default value"

    # Code: ARG build_type=development FROM base_image AS builder RUN if [ "$build_type" = "production" ]; then \ # Production build steps \ else \ # Development build steps \ fi

    Description: This Dockerfile sets a default value for the build_type argument, allowing users to override it during the build process. If not specified, the default value is used.

  3. "Dockerfile ARG if-else condition with multi-stage builds"

    # Code: ARG build_type=development # Stage 1: Build stage FROM base_image AS builder RUN if [ "$build_type" = "production" ]; then \ # Production build steps \ else \ # Development build steps \ fi # Stage 2: Final stage FROM another_image AS final COPY --from=builder /app /app

    Description: This Dockerfile demonstrates a multi-stage build with a conditional ARG. The build steps are conditionally executed based on the value of build_type.

  4. "Dockerfile if-else condition based on build arguments"

    # Code: ARG build_type FROM base_image AS builder RUN case "$build_type" in \ production) \ # Production build steps ;; \ development) \ # Development build steps ;; \ *) \ # Default build steps ;; \ esac

    Description: This Dockerfile uses a case statement to conditionally execute build steps based on the value of the build_type argument, with a default case if none of the specified values match.

  5. "Dockerfile if-else condition based on multiple ARG values"

    # Code: ARG build_type ARG environment FROM base_image AS builder RUN if [ "$build_type" = "production" ] && [ "$environment" = "production" ]; then \ # Production build steps \ else \ # Development build steps \ fi

    Description: This Dockerfile uses multiple ARG values (build_type and environment) to conditionally execute build steps based on their combination.

  6. "Dockerfile conditional ARG for setting environment variables"

    # Code: ARG build_type FROM base_image AS builder ENV ENV_VAR_NAME= \ $(if [ "$build_type" = "production" ]; then \ echo "production_value"; \ else \ echo "development_value"; \ fi)

    Description: This Dockerfile sets an environment variable (ENV_VAR_NAME) conditionally based on the value of the build_type argument.

  7. "Dockerfile ARG if-else with default values for environment variables"

    # Code: ARG build_type=development FROM base_image AS builder ENV ENV_VAR_NAME= \ $(if [ "$build_type" = "production" ]; then \ echo "production_value"; \ else \ echo "development_value"; \ fi)

    Description: This Dockerfile sets a default value for the build_type argument, and the environment variable is set accordingly based on the specified or default value.

  8. "Dockerfile ARG if-else for conditional installation of packages"

    # Code: ARG build_type FROM base_image AS builder RUN if [ "$build_type" = "production" ]; then \ apt-get install -y production_package; \ else \ apt-get install -y development_package; \ fi

    Description: This Dockerfile conditionally installs different packages based on the value of the build_type argument.

  9. "Dockerfile ARG if-else with conditional COPY"

    # Code: ARG build_type FROM base_image AS builder COPY $(if [ "$build_type" = "production" ]; then \ echo production_files; \ else \ echo development_files; \ fi) /app

    Description: This Dockerfile uses a conditional COPY command to copy different sets of files based on the value of the build_type argument.

  10. "Dockerfile ARG if-else condition for setting entrypoint"

    # Code: ARG build_type FROM base_image AS builder ENTRYPOINT $(if [ "$build_type" = "production" ]; then \ echo "production_entrypoint"; \ else \ echo "development_entrypoint"; \ fi)

    Description: This Dockerfile conditionally sets the entrypoint based on the value of the build_type argument. The entrypoint is different for production and development builds.

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