Docker

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Contents:

Installation #

MacOS #

brew cask install docker

Basic usage #

Running a container interactively #

Pulling an existing from the repository:

docker pull nats:latest

Then to run this image in a container:

docker run -p 4222:4222 -ti nats:latest

Params used:

  • -p: publishes a container’s port (a mapping from container to host)
  • -i: keep STDIN open even if not attached — this means <cmd> | docker run works
  • -t: allocates a pseudo-TTY, which in combination with -i means we can interact with the process

Running a container as daemon #

For this we add the -d option:

docker run -p 4222:4222 -d -ti nats:latest

List containers #

List active containers:

docker ps --no-trunc

List all containers:

docker ps -a

Start & stop containers #

Stops container with the id <containerid>:

docker stop <containerid>

Stops all running containers:

docker stop $(docker ps -a -q)

To re-start a certain container:

docker start <containerid>

Remove containers #

docker rm <container_id>

Remove all containers:

docker rm $(docker ps -a -q)

If some containers are still running as a daemon, use -f (force):

docker rm -f $(docker ps -a -q)

Remove orphan volumes #

List:

docker volume ls -qf dangling=true

Remove:

docker volume rm $(docker volume ls -qf dangling=true)

List or remove images #

List images available locally:

docker images

Remove all images:

docker rmi $(docker images -q -a)

List or remove volumes #

docker volume ls

To remove:

docker volume rm <id>

Remove all volumes:

docker volume rm $(docker volume ls -q)

Gain shell access to a container #

docker exec -it <container_id> sh

Building Docker images #

Resources:

Auto-update containers to latest #

Run watchtower container, with option to auto update only labelled containers:

docker run -d \
  --restart=always \
  --name=watchtower \
  -v /var/run/docker.sock:/var/run/docker.sock \
  containrrr/watchtower \
  --label-enable

If using docker-compose:

watchtower:
  container_name: watchtower
  image: 'containrrr/watchtower:latest'
  restart: unless-stopped
  volumes:
    - /var/run/docker.sock:/var/run/docker.sock
  restart: unless-stopped
  networks:
    - main
  command: --label-enable

To mark images for auto-updating:

docker run -d --label=com.centurylinklabs.watchtower.enable=true someimage

Or if using docker-compose:

version: '3'

services:
  app:
    image: 'someimage'
    restart: always
    labels:
      - "com.centurylinklabs.watchtower.enable=true"

Watchtower will check periodically for newer images and will restart services/containers with new image.

Docker Compose #

See docs for installing.

brew install docker-compose

Given a docker-compose.yml in the current directory, starting all containers:

docker-compose up

Or to start them as a daemons (in the background):

docker-compose up -d

Example docker-compose.yml #

version: "3.7"

services:
  nats:
    image: nats-streaming:latest
    entrypoint:
    - /nats-streaming-server
    - -cid
    - amethyst-cluster
    ports:
    - "4222:4222"
    - "8222:8222"
    - "6222:6222"
    restart: always
    tty: true
    networks:
      - main

  mysql:
    image: mysql:8.0
    ports:
      - "3306:3306"
    restart: always
    tty: true
    environment:
      MYSQL_DATABASE: mydb
      MYSQL_USER: myuser
      MYSQL_PASSWORD: mypass
      MYSQL_ROOT_PASSWORD: root
    volumes:
      - db-data:/var/lib/mysql
    networks:
      - main

  redis:
    image: redis:latest
    ports:
      - "6379:6379"
    restart: always
    tty: true
    networks:
      - main

  myimage:
    image: myorganization/myimage:latest
    build: .
    depends_on:
      - nats
      - mysql
      - redis
    environment:
      ENV: stage
      LANG: C.UTF-8
      NATS_SERVERS: "nats://nats:4222"
      VOLUME_PATH: "/tmp/dont_care"
    networks:
      - main
    command: bash /path/to/custom-command.sh
    volumes:
      - .:/tmp/dont_care

volumes:
  db-data:

networks:
  main:
    external:
      name: main