Get Started, Part 1: Orientation and setupEstimated reading time: 4 minutes
Welcome! We are excited that you want to learn Docker. The Docker Get Started Tutorial teaches you how to:
- 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 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.
Prepare your Docker environment
For full Kubernetes Integration
Test Docker version
docker --versionand ensure that you have a supported version of Docker:
docker --version Docker version 17.12.0-ce, build c97c6d6
--) 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 ...
To avoid permission errors (and the use of
sudo), add your user to the
dockergroup. Read more.
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. ...
hello-worldimage that was downloaded to your machine:
docker image ls
hello-worldcontainer (spawned by the image) which exits after displaying its message. If it were still running, you would not need the
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, setup, orientation, quickstart, intro, concepts, containers