Docker 101: .dockerignore

Mar 04, 2023 · 1 min read · Post a comment

A Dockerfile specifies the instructions for building a Docker image, which is essentially a packaged version of a software application along with its dependencies. However, when building a Docker image, you may not want to include all the files and directories from the application codebase. This is where a .dockerignore file comes into play.


  • Docker


A .dockerignore file is a text file that instructs Docker which files and directories to exclude from the build itself when creating a Docker image.

The syntax of a .dockerignore file is similar to that of a .gitignore file, where you specify patterns of files and directories to exclude. For example, you might want to exclude files that are generated by the build process, such as log files, cache files, or temporary files. There is a GitHub repository out there for each dockerized app, google it.

When building a Docker image, Docker reads the .dockerignore file and uses it to exclude files and directories from the build. This can speed up the build process and reduce the size of the resulting image, as unnecessary files are not included. Less files, less size, and better security, in a way.


Overall, a .dockerignore file is a configuration file used to exclude files and directories from the docker build operation when creating a Docker image. This file works in jointly with the Dockerfile to help create a smaller and more efficient Docker image.

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