Dockerfile Best Practices: Alpine Images, Multi‑Stage Builds, ARG, CMD/ENTRYPOINT, and COPY vs ADD

Docker is a container technology that creates isolated environments on a host OS, allowing independent installation of software and services.

Port mapping ( -p ) and volume mounting ( -v ) connect host ports and directories to containers.

Example command:

docker run -p 3000:3000 -v /aaa:/bbb/ccc --name xxx-container xxx-image

Docker images are built from Dockerfiles using docker build and run with docker run . A typical workflow includes building the image, pushing to a registry, and pulling for deployment.

To reduce image size, replace the default Debian‑based image with a lightweight Alpine base, e.g., node:18-alpine3.14 , which can shrink the image by hundreds of megabytes.

Multi‑stage builds separate the build environment from the runtime image, copying only the compiled dist folder and production dependencies, dramatically decreasing final image size.

Build‑time arguments ( ARG ) allow passing variables during docker build , which can be set as runtime environment variables ( ENV ) inside the container.

Using CMD provides a default command that can be overridden at docker run time, while ENTRYPOINT defines an immutable command; combining both gives flexible defaults.

The COPY instruction copies files as‑is, whereas ADD also extracts tar archives automatically.

Use Alpine base images for smaller size.

Apply multi‑stage builds to keep only necessary artifacts.

Leverage ARG for build flexibility and ENV for runtime variables.

Prefer CMD for overridable defaults; combine with ENTRYPOINT when needed.

Use COPY for regular file copying and ADD only when archive extraction is required.