What is the difference between `docker-compose build` and `docker build`?

Question

What is the difference between docker-compose build and docker build?

Suppose in a dockerized project path there is a docker-compose.yml file:

docker-compose build

And

docker build

Answer 1

docker-compose can be considered a wrapper around the docker CLI (in fact it is another implementation in python as said in the comments) in order to gain time and avoid 500 characters-long lines (and also start multiple containers at the same time). It uses a file called docker-compose.yml in order to retrieve parameters.

You can find the reference for the docker-compose file format here.

So basically docker-compose build will read your docker-compose.yml, look for all services containing the build: statement and run a docker build for each one.

Each build can specify a Dockerfile, a context and args to pass to docker.

To conclude with an example docker-compose.yml file:

version: '3.2'

services:
  database:
    image: mariadb
    restart: always
    volumes:
      - ./.data/sql:/var/lib/mysql

  web:
    build:
      dockerfile: Dockerfile-alpine
      context: ./web
    ports:
      - 8099:80
    depends_on:
      - database 

When calling docker-compose build, only the web target will need an image to be built. The docker build command would look like:

docker build -t web_myproject -f Dockerfile-alpine ./web