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

Solution 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

Solution 2:

docker-compose build will build the services in the docker-compose.yml file.

https://docs.docker.com/compose/reference/build/

docker build will build the image defined by Dockerfile.

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

Solution 3:

Basically, docker-compose is a better way to use docker than just a docker command.

If the question here is if docker-compose build command, will build a zip kind of thing containing multiple images, which otherwise would have been built separately with usual Dockerfile, then the thinking is wrong.

Docker-compose build, will build individual images, by going into individual service entry in docker-compose.yml.

With docker images, command, we can see all the individual images being saved as well.

The real magic is docker-compose up.

This one will basically create a network of interconnected containers, that can talk to each other with name of container similar to a hostname.