What is Docker-compose?

 

Docker-compose:

If you’re building an application out of processes in multiple containers that all reside on the same host, you can use Docker Compose to manage the application’s architecture. Docker Compose creates a YAML file that specifies which services are included in the application, and can deploy and run containers with a single command. Using Docker Compose, you can also define persistent volumes for storage, specify base nodes, and document and configure service dependencies.

docker-compose.yml is the default filename but can be used with docker-compose -f.

Docker-compose is a tool for defining and running multi-container Docker applications.

Note: Docker compose is not for the production-grade deployment. It's for the local testing.

docker-compose.yml template file:

version: '3.1'       # if no version is specified then v1 is assumed. Recommend v2 minimum

services:  # containers. same as docker run

  servicename: # a friendly name. this is also DNS name inside network

    image: # Optional if you use build:

    command:         # Optional, replace the default CMD specified by the image

    environment:         # Optional, same as -e in docker run

    volumes:         # Optional, same as -v in docker run

  servicename2:

volumes: # Optional, same as docker volume create

networks: # Optional, same as docker network create

Run the below command to read the docker-compose file and start all the containers. This will run in the foreground.

$ sudo docker-compose up

With the "-d" option it will run in the background.

$ sudo docker-compose up -d

To stop all the containers and remove the volumes and networks, run the below command.

$ sudo docker-compose down

The "-v" option will remove the created volumes. "-rmi local" will remove any images created via docker-compose file.

$ sudo docker-compose down -v -rmi local

To show the logs of the containers.

$ sudo docker-compose logs

To show the container processes on the host and their ip, port, state.

$ sudo docker-compose ps

To show the processes running inside each container of docker-compose.

$ sudo docker-compose top

To rebuild the image from the Dockerfile mentioned in the docker-compose file and starts all the services with the mentioned config.

$ sudo docker-compose build

Example1: docker-compose.yml

Here we are creating two containers with four volumes.

version: '3'

services:

  drupal:

    image: drupal

    ports:

      - 8080:80

    volumes:

      - drupal-modules:/var/www/html/modules

      - drupal-profiles:/var/www/html/profiles

      - drupal-themes:/var/www/html/themes

      - drupal-sites:/var/www/html/sites

  postgres:

    image: postgres

    environment:

      POSTGRES_PASSWORD: password

volumes:

    drupal-modules:

    drupal-profiles:

    drupal-themes:

    drupal-sites:

Example2: docker-compose.yml

version: '2'

services:

  proxy:

    build:

      context: .

      dockerfile: nginx.Dockerfile

    ports:

      - '80:80'

  web:

    image: httpd

    volumes:

      - ./html:/usr/local/apache2/htdocs/

nginx.Dockerfile (file contents):

FROM nginx:1.13

COPY nginx.conf /etc/nginx/conf.d/default.conf

nginx.conf file (file contents):

server {

listen 80;

location / {

proxy_pass         http://web;

proxy_redirect     off;

proxy_set_header   Host $host;

proxy_set_header   X-Real-IP $remote_addr;

proxy_set_header   X-Forwarded-For $proxy_add_x_forwarded_for;

proxy_set_header   X-Forwarded-Host $server_name;

}

}