Get Docker

Overview of Docker editions

Docker is available in two editions:

Community Edition (CE)
Enterprise Edition (EE)

Docker CE

About Docker CE

Docker Community Edition (CE) is ideal for developers and small teams looking to get started with Docker and experimenting with container-based apps. Docker CE has three types of update channels, stable, test, and nightly:

Stable gives you latest releases for general availability.
Test gives pre-releases that are ready for testing before general availability.
Nightly gives you latest builds of work in progress for the next major release.

Cloud

Docker for AWS

Docker for Azure

Get started

Get Started, Part 1: Orientation and setup

Set up your Docker environment (on this page)
Build an image and run it as one container
Scale your app to run multiple containers
Distribute your app across a cluster
Stack services by adding a backend database
Deploy your app to production

Docker concepts

Docker is a platform for developers and sysadmins to develop, deploy, and run applications with containers. The use of Linux containers to deploy applications is called containerization. Containers are not new, but their use for easily deploying applications is.

Containerization is increasingly popular because containers are:

Flexible: Even the most complex applications can be containerized.
Lightweight: Containers leverage and share the host kernel.
Interchangeable: You can deploy updates and upgrades on-the-fly.
Portable: You can build locally, deploy to the cloud, and run anywhere.
Scalable: You can increase and automatically distribute container replicas.
Stackable: You can stack services vertically and on-the-fly.

Images and containers

A container is launched by running an image. An image is an executable package that includes everything needed to run an application–the code, a runtime, libraries, environment variables, and configuration files.

A container is a runtime instance of an image–what the image becomes in memory when executed (that is, an image with state, or a user process). You can see a list of your running containers with the command, docker ps, just as you would in Linux.

Containers and virtual machines

A container runs natively on Linux and shares the kernel of the host machine with other containers. It runs a discrete process, taking no more memory than any other executable, making it lightweight.

By contrast, a virtual machine (VM) runs a full-blown “guest” operating system with virtual access to host resources through a hypervisor. In general, VMs provide an environment with more resources than most applications need.

docker

Test Docker version

Run docker –version and ensure that you have a supported version of Docker:

docker --version

Docker version 17.12.0-ce, build c97c6d6

Run docker info or (docker version without –) to view even more details about your docker installation:

docker info

Containers: 0
 Running: 0
 Paused: 0
 Stopped: 0
Images: 0
Server Version: 17.12.0-ce
Storage Driver: overlay2
...

Test Docker installation

Test that your installation works by running the simple Docker image, hello-world:

docker run hello-world

Unable to find image 'hello-world:latest' locally
latest: Pulling from library/hello-world
ca4f61b1923c: Pull complete
Digest: sha256:ca0eeb6fb05351dfc8759c20733c91def84cb8007aa89a5bf606bc8b315b9fc7
Status: Downloaded newer image for hello-world:latest

Hello from Docker!
This message shows that your installation appears to be working correctly.
...

List the hello-world image that was downloaded to your machine:

docker image ls

List the hello-world container (spawned by the image) which exits after displaying its message. If it were still running, you would not need the –all option:

docker container ls --all

CONTAINER ID     IMAGE           COMMAND      CREATED            STATUS
54f4984ed6a8     hello-world     "/hello"     20 seconds ago     Exited (0) 19 seconds ago

Recap and cheat sheet

## List Docker CLI commands
docker
docker container --help

## Display Docker version and info
docker --version
docker version
docker info

## Execute Docker image
docker run hello-world

## List Docker images
docker image ls

## List Docker containers (running, all, all in quiet mode)
docker container ls
docker container ls --all
docker container ls -aq

Conclusion of part one

Containerization makes CI/CD seamless. For example:

applications have no system dependencies updates can be pushed to any part of a distributed application resource density can be optimized. With Docker, scaling your application is a matter of spinning up new executables, not running heavy VM hosts.

Get started with Docker

Orientation