.dockerignore

A .dockerignore file at the root of the build context lists files that are never sent to the builder. It keeps images small and keeps secrets out of them.

How it works

It uses patterns like .gitignore: node_modules, .git, *.log, .env. A line starting with ! brings a file back. Ignored files are invisible to COPY and ADD, so COPY . . can no longer pick them up by accident.

What breaks

It must sit at the root of the context: a .dockerignore next to a Dockerfile in another folder is ignored. And ignoring a file that the Dockerfile copies by name, like package-lock.json, makes the build fail with "not found".

In .dockerignore

node_modules
.git
*.log
.env
.env.*
!.env.example

See it break, then fix it

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