What is context: . in docker-compose?

Question

I am trying learn docker and created my first docker compose file. Basically I am trying to create a Django web microservice and use docker compose file to manage it. Here is my code for my docker-compose.yml:

version: "3"

services:
  app:
    build:
      context: .
    ports:
      - "8000:8000"
    volumes:
      - ./app:/app
    command: >
      sh -c "py manage.py runserver 0.0.0.0:8000"

I don't understand the use of context: . Can someone please explain me this

[How to include files outside of Docker's build context?](https://stackoverflow.com/questions/27068596/how-to-include-files-outside-of-dockers-build-context) includes some examples of cases where you will need to specify a different `context:` directory. — David Maze, Jan 08 '21 at 03:03
Does this answer your question? [What is happening when using ../ with docker-compose volume](https://stackoverflow.com/questions/51049460/what-is-happening-when-using-with-docker-compose-volume) — NotTheDr01ds, Jan 08 '21 at 03:13
Also, when providing no other attributes: you can provide the context to build directly: `build: .` — Chris Becke, Jan 08 '21 at 08:06

score 25 · Accepted Answer · edited Nov 18 '21 at 16:11

CONTEXT

Either a path to a directory containing a Dockerfile, or a url to a git repository.

When the value supplied is a relative path, it is interpreted as relative to the location of the Compose file. This directory is also the build context that is sent to the Docker daemon.

Compose builds and tags it with a generated name, and uses that image thereafter.

build:
  context: ./dir

That mean, its a path to the directory that contains Dockerfile file. It purposes to build a new image for the service.

Reference: https://docs.docker.com/compose/compose-file/compose-file-v3/

In your case:

   context: .

Dockerfile file should be existing in the current directory (in the same folder of the docker-compose.yml file).

What is context: . in docker-compose?

1 Answers1