Introduction

In my previous blog, I talked about the differences between containers and traditional virtual machines. Docker’s technology is unique because it focuses on the requirements of developers and systems operators to separate application dependencies from infrastructure.

Success in the Linux world also drove a partnership with Microsoft that brought Docker containers and its functionality to Windows Server (sometimes referred to as Docker Windows containers). In this article, I first talk briefly about Docker components and tools and then share installation steps. But you can use this link if you would like to skip to the installation steps.

Docker Components and tools :

Docker can package an application and its dependencies in a virtual container that can run on any Linux, Windows, or macOS computer. This enables the application to run in a variety of locations, such as on-premises, in a public cloud, and/or in a private cloud. When running on Linux, Docker uses the resource isolation features of the Linux kernel (such as cgroups and kernel namespaces) and a union-capable file system (such as OverlayFS) to allow containers to run within a single Linux instance, avoiding the overhead of starting and maintaining virtual machines. Docker on macOS uses a Linux virtual machine to run the containers.

Components

The Docker software as a service offering consists of three components:

  • Software: The Docker daemon, called dockerd, is a persistent process that manages Docker containers and handles container objects. The daemon listens for requests sent via the Docker Engine API. The Docker client program, called docker, provides a command-line interface, CLI, that allows users to interact with Docker daemons.
  • Objects: Docker objects are various entities used to assemble an application in Docker. The main classes of Docker objects are images, containers, and services.
    • A Docker container is a standardized, encapsulated environment that runs applications. A container is managed using the Docker API or CLI.
    • A Docker image is a read-only template used to build containers. Images are used to store and ship applications.
    • A Docker service allows containers to be scaled across multiple Docker daemons. The result is known as a swarm, a set of cooperating daemons that communicate through the Docker API.
  • Registries: A Docker registry is a repository for Docker images. Docker clients connect to registries to download (“pull”) images for use or upload (“push”) images that they have built. Registries can be public or private. Two main public registries are Docker Hub and Docker Cloud. Docker Hub is the default registry where Docker looks for images. Docker registries also allow the creation of notifications based on events. In this blog I explain how you can setup your secure private docker registry with UI.

Tools

  • Docker Compose is a tool for defining and running multi-container Docker applications. It uses YAML files to configure the application’s services and performs the creation and start-up process of all the containers with a single command. The docker-compose CLI utility allows users to run commands on multiple containers at once, for example, building images, scaling containers, running containers that were stopped, and more. Commands related to image manipulation, or user-interactive options, are not relevant in Docker Compose because they address one container. The docker-compose.yml file is used to define an application’s services and includes various configuration options. For example, the build option defines configuration options such as the Dockerfile path, the command option allows one to override default Docker commands, and more.
  • Docker Swarm provides native clustering functionality for Docker containers, which turns a group of Docker engines into a single virtual Docker engine. In Docker 1.12 and higher, Swarm mode is integrated with Docker Engine. The docker swarm CLI utility allows users to run Swarm containers, create discovery tokens, list nodes in the cluster, and more. The docker node CLI utility allows users to run various commands to manage nodes in a swarm, for example, listing the nodes in a swarm, updating nodes, and removing nodes from the swarm. Docker manages swarms using the Raft consensus algorithm. According to Raft, for an update to be performed, the majority of Swarm nodes need to agree on the update.
  • Docker Volume If you copy or create a file in a container, when you stop that container that file (and any other files created or copied) will be deleted. Docker Volume is a solution for this issue. Volumes are the preferred mechanism for persisting data generated by and used by Docker containers. 

Script to install docker and docker-compose on Ubuntu

Below script adds all the required repositories and installs dependencies as well. You can paste and run it as-it-is for setting up docker and docker-compose

sudo apt-get update
sudo apt-get -y install \
    apt-transport-https \
    ca-certificates \
    curl \
    gnupg \
    lsb-release
	
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /usr/share/keyrings/docker-archive-keyring.gpg
echo \
  "deb [arch=amd64 signed-by=/usr/share/keyrings/docker-archive-keyring.gpg] https://download.docker.com/linux/ubuntu \
  $(lsb_release -cs) stable" | sudo tee /etc/apt/sources.list.d/docker.list > /dev/null
sudo apt-get update
sudo apt-get install -y docker-ce docker-ce-cli containerd.io
sudo curl -L "https://github.com/docker/compose/releases/download/1.27.4/docker-compose-$(uname -s)-$(uname -m)" -o /usr/local/bin/docker-compose
sudo chmod +x /usr/local/bin/docker-compose