Docker Build Command

The docker build command is a tool in a developer's arsenal, enabling them to create Docker images from a Dockerfile and a build context. This article delves into the intricacies of the command, its various options, and how to use them effectively.

Basic Syntax

The basic syntax of the docker build command is as follows:

$ docker build [OPTIONS] PATH | URL | -

OPTIONS are optional flags, PATH is the local directory containing the Dockerfile and build context, URL is the remote repository with the Dockerfile, and - indicates that the build context is provided via STDIN.

Specifying the Build Context

The build context is a crucial part of the build process. It consists of the files and directories required for the Dockerfile to execute its instructions. By default, the build context is the current directory where the docker build command is run. To specify a different build context, provide the path as an argument:

$ docker build -t my-image:latest /path/to/build/context

Tagging Images

Using the -t or --tag flag, you can assign a human-readable tag to the resulting image. This is helpful for organizing and managing your images. Tags follow the format repository:tag:

$ docker build -t my-image:latest .

Build Cache and Layer Reuse

Docker caches intermediate layers during the build process to optimize and speed up subsequent builds. To force a cache miss and ensure all layers are built from scratch, use the --no-cache flag:

$ docker build --no-cache -t my-image:latest .

Build Arguments

Build arguments allow you to pass values to your Dockerfile at build time. Use the --build-arg flag followed by the argument and its value:

$ docker build --build-arg API_KEY=myapikey -t my-image:latest .

Using Multi-Stage Builds

Multi-stage builds are a way to optimize your Docker images by only including the necessary files and dependencies in the final image. To utilize multi-stage builds, use the --target flag followed by the target stage:

$ docker build --target production -t my-image:latest .

Debugging Build Failures

When a build fails, it can be challenging to pinpoint the cause. Use the --progress flag to display a more detailed build progress:

$ docker build --progress=plain -t my-image:latest .

References

https://docs.docker.com/engine/reference/commandline/build/