5.1.2.3 Dockerignore Local Config

Excluding local configuration through .dockerignore prevents developer-specific or environment-specific configuration files — IDE settings, local override files, personal environment variables — from being unnecessarily included in the build context or accidentally copied into the resulting image.

What Counts as Local Configuration

Local configuration typically includes anything specific to an individual developer's machine or personal setup, rather than configuration genuinely needed by the application itself inside the container.

.vscode/
.idea/
*.local.json
docker-compose.override.yml

Why Local Configuration Shouldn't Be in the Image

Local, developer-specific configuration files have no relevance to how the application runs inside a container, and including them unnecessarily bloats the image and could even leak personal or machine-specific details that have no business being part of a shared, distributed artifact.

.vscode/

A developer's personal editor settings, for instance, serve no purpose to anyone running the resulting container and should never end up inside it.

Distinguishing Local Config From Application Config

Configuration the application genuinely needs at runtime — a default configuration file the application reads — is different from purely local, developer-convenience configuration, and only the former typically belongs inside the image.

COPY config/default.yaml /app/config/

This kind of application configuration is appropriately included; a developer's local .vscode/settings.json is not.

Verifying No Local Configuration Leaked Into an Image

Periodically checking a built image's contents for unexpected local configuration files helps catch an incomplete .dockerignore before it becomes a recurring habit.

docker run --rm myapp find / -name ".vscode" -o -name ".idea"

Why Excluding Local Configuration Matters

Keeping developer-specific configuration out of both the build context and the final image keeps the resulting artifact clean, free of irrelevant personal details, and consistent regardless of which developer's machine happened to produce a given build.