Docker Overview & Sytax Guide

Overview

1. Dockerfile

• A text file that contains a set of instructions used to build a Docker image.
• Each instruction in the Dockerfile represents a layer in the resulting image.
• Define what goes on in the environment inside your container and specify how to configure the container, install dependencies, and set up the application environment.

Dockerfile

2. Docker image

• A read-only template that contains a set of instructions for creating a Docker container.
• Essentially a snapshot of a Docker container in a particular time.
• Includes the filesystem and configuration needed to run a specific application.
• Built from a Dockerfile and can be stored in repositories such as Docker Hub.

3. Docker container

• An isolated environment for your code.
• Not depend on your OS or your files.
• Have everything (code, runtime, libraries, dependencies, and configurations) that your code needs in order to run.
• Share the host operating system’s kernel, making them portable and efficient.
• Can be started, stopped, moved, and deleted with ease.

Docker Container

From Dockerfile to Docker container.

4. Docker volume

• Docker containers are indeed designed to be ephemeral, meaning they are intended to be short-lived and disposable → Docker volume.
• A persistent data storage mechanism used by Docker containers to store and manage data independently of the container’s lifecycle.
• Allow data to survive container restarts and can be shared and reused among multiple containers.

Docker mount and volume.

How does Docker volume work?

5. Docker network

• Provides a way to let containers in docker isolate but can communicate from one to another.
• When Docker is installed on the system, it automatically creates 3 networks: bridge, host and none.
• Docker automatically creates a default bridge network (docker0) for communication among containers on the same host.
• You can also define custom Docker networks to isolate and secure communication between containers or connect containers to external networks.

Docker network example

6. Docker Compose

• A tool for defining and running multi-container Docker applications.
• Uses a YAML file (docker-compose.yml) to define the services (containers), networks, and volumes that make up the application stack.
• Simplifies the complex task of orchestrating and coordinating various services, making it easier to manage and replicate your application environment.

Docker Syntax Guide

Docker Commands

*Note: All options and sub-commands listed below are just a small portion, provided based on usage needs. You can print the help screen of any sub-command with syntax:

docker <subcommand> --help

• docker run

  • docker run [OPTIONS] IMAGE [COMMAND] [ARG…]
  • Description: Create and start a new container based on the specified IMAGE.
  • Options:
    • -d: Run container in detached mode (background).
    • -it: Interactive mode with a pseudo-TTY (for running interactive shells).
    • –name: Assign a name to the container.
    • –rm: Automatically remove the container when it exits.
    • -e: Set environment variables.
    • -p: Publish container’s ports to the host.
    • -v: Mount host volumes into the container.
    • –entrypoint: Override the entry point of the Docker image.

• docker build

  • docker build [OPTIONS] PATH | URL | -
  • Description: Build a Docker image from a Dockerfile.
  • Options:
    • -t: Name and optionally a tag in the ’name:tag’ format.
    • –file: Name of the Dockerfile (default is ‘PATH/Dockerfile’).

• docker images

  • docker images [OPTIONS] [REPOSITORY[:TAG]]
  • Description: List Docker images.
  • Options:
    • -a: Show all images (including intermediate images).
    • –digests: Show digests.

• docker ps

  • docker ps [OPTIONS]
  • Description: List containers.
  • Options:
    • -a: Show all containers (including stopped ones).
    • -q: Only display container IDs.
    • –filter: Filter output based on conditions.

• docker exec

• docker exec [OPTIONS] CONTAINER COMMAND [ARG…]

  • Description: Execute a command inside a running container.
  • Options:
    • -it: Interactive mode with a pseudo-TTY.
    • -e: Set environment variables.

• docker stop

  • docker stop [OPTIONS] CONTAINER [CONTAINER…]
  • Description: Stop one or more running containers.
  • Options:
    • -t: Timeout in seconds to wait for stop (default 10).

• docker rm

  • docker rm [OPTIONS] CONTAINER [CONTAINER…]
  • Description: Remove one or more containers.
  • Options:
    • -f: Force removal of running container.

• docker rmi

  • docker rmi [OPTIONS] IMAGE [IMAGE…]
  • Description: Remove one or more images.
  • Options:
    • -f: Force removal of the image.

• docker pull

  • docker pull [OPTIONS] NAME[:TAG|@DIGEST]
    • Description: Pull an image or a repository from a registry.
    • Options:
      • –all-tags: Download all tagged images in the repository.

Docker Compose

• docker-compose up

  • docker-compose up [OPTIONS] [SERVICE…]
  • Description: Create and start containers defined in the Compose file.
  • Options:
    • –build: Build images before starting containers.
    • -d: Detached mode.

• docker-compose down

  • docker-compose down [OPTIONS]
    • Description: Stop and remove containers, networks, and volumes defined in the Compose file.
    • Options:
      • –volumes: Remove named volumes declared in the volumes section of the Compose file.

Docker Swarm

• docker swarm init

  • docker swarm init [OPTIONS]
  • Description: Initialize a new Docker Swarm.
  • Options:
    • –advertise-addr: Advertised address (format: <ip|interface>[:port]).

• docker service

  • docker service COMMAND [OPTIONS]
  • Description: Manage Docker services in a Swarm.
  • Commands:
    • create: Create a new service.
    • ls: List services.
    • scale: Scale one or multiple replicated services.

Docker Network

• docker network
  • docker network COMMAND [OPTIONS]
    • Description: Manage Docker networks.
    • Commands:
      • create: Create a new network.
      • ls: List networks.
      • connect: Connect a container to a network.
      • disconnect: Disconnect a container from a network.

Docker Volumes

• docker volume
  • docker volume COMMAND [OPTIONS]
    • Description: Manage Docker volumes.
    • Commands:
      • create: Create a volume.
      • ls: List volumes.
      • inspect: Display detailed information about a volume.

Docker Registry (Docker Hub)

• docker login

  • docker login [OPTIONS] [SERVER]
  • Description: Log in to a Docker registry.
  • Options:
    • –username: Username.
    • –password: Password.

• docker push (Login required)

  • docker push [OPTIONS] NAME[:TAG]
  • Description: Push an image or a repository to a registry.

• docker pull (No login required)

  • docker pull [OPTIONS] NAME[:TAG]
  • Description: Pull an image or a repository from a registry.

Docker System

• docker system
  • docker system COMMAND [OPTIONS]
  • Description: Manage Docker system resources.
  • Commands:
    • df: Show Docker disk usage.
    • prune: Remove unused data.