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Update part 1 (#5806)
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Gwendolynne Barr
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{% include_relative nav.html selected="1" %}
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Welcome! We are excited you want to learn how to use Docker.
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Welcome! We are excited that you want to learn Docker. The _Docker Get Started Tutorial_
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teaches you how to:
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In this six-part tutorial, you will:
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1. Set up your Docker environment (on this page)
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2. [Build an image and run it as one container](part2.md)
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3. [Scale your app to run multiple containers](part3.md)
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4. [Distribute your app across a cluster](part4.md)
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5. [Stack services by adding a backend database](part5.md)
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6. [Deploy your app to production](part6.md)
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1. Get set up and oriented, on this page.
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2. [Build and run your first app](part2.md)
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3. [Turn your app into a scaling service](part3.md)
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4. [Span your service across multiple machines](part4.md)
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5. [Add a visitor counter that persists data](part5.md)
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6. [Deploy your swarm to production](part6.md)
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## Docker concepts
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The application itself is very simple so that you are not too distracted by
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what the code is doing. After all, the value of Docker is in how it can build,
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ship, and run applications; it's totally agnostic as to what your application
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actually does.
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Docker is a platform for developers and sysadmins to **develop, deploy, and run**
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applications with containers. The use of Linux containers to deploy applications
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is called _containerization_. Containers are not new, but their use for easily
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deploying applications is.
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## Prerequisites
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Containerization is increasingly popular because containers are:
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While we define concepts along the way, it is good for you to understand
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[what Docker is](https://www.docker.com/what-docker) before we begin.
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- Flexible: Even the most complex applications can be containerized.
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- Lightweight: Containers leverage and share the host kernel.
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- Interchangeable: You can deploy updates and upgrades on-the-fly.
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- Portable: You can build locally, deploy to the cloud, and run anywhere.
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- Scalable: You can increase and automatically distribute container replicas.
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- Stackable: You can stack services vertically and on-the-fly.
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We also need to assume you are familiar with a few concepts before we continue:
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{:width="300px"}
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- IP Addresses and Ports
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- Virtual Machines
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- Editing configuration files
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- Basic familiarity with the ideas of code dependencies and building
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- Machine resource usage terms, like CPU percentages, RAM use in bytes, etc.
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### Images and containers
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Finally, though we remind you again when you need these things, you can
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save yourself some distraction at that time by [signing up for a
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Docker ID](https://cloud.docker.com) and using it on your local machine
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by running the following command:
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A container is launched by running an image. An **image** is an executable
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package that includes everything needed to run an appplication--the code, a
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runtime, libraries, environment variables, and configuration files.
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```
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docker login
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```
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A **container** is a runtime instance of an image--what the image becomes in
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memory when executed (that is, an image with state, or a user process). You can
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see a list of your running containers with the command, `docker ps`, just as you
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would in Linux.
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## A brief explanation of containers
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### Containers and virtual machines
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An **image** is a lightweight, stand-alone, executable package that includes
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everything needed to run a piece of software, including the code, a runtime,
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libraries, environment variables, and config files.
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A **container** runs _natively_ on Linux and shares the kernel of the host
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machine with other containers. It runs a discrete process, taking no more memory
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than any other executable, making it lightweight.
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A **container** is a runtime instance of an image—what the image becomes
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in memory when actually executed. It runs completely isolated from the host
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environment by default, only accessing host files and ports if configured to do
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so.
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By contrast, a **virtual machine** (VM) runs a full-blown "guest" operating
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system with _virtual_ access to host resources through a hypervisor. In general,
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VMs provide an environment with more resources than most applications need.
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Containers run apps natively on the host machine's kernel. They have better
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performance characteristics than virtual machines that only get virtual access
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to host resources through a hypervisor. Containers can get native access, each
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one running in a discrete process, taking no more memory than any other
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executable.
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{:width="300px"} | {:width="300px"}
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## Containers vs. virtual machines
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## Prepare your Docker environment
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Consider this diagram comparing virtual machines to containers:
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Install a [maintained version](https://docs.docker.com/engine/installation/#updates-and-patches){: target="_blank" class="_"}
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of Docker Community Edition (CE) or Enterprise Edition (EE) on a
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[supported platform](https://docs.docker.com/engine/installation/#supported-platforms){: target="_blank" class="_"}.
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### Virtual Machine diagram
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> For full Kubernetes Integration
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>
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> - [Kubernetes on Docker for Mac](https://docs.docker.com/docker-for-mac/kubernetes/){: target="_blank" class="_"}
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is available in
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[17.12.0-ce Edge](https://docs.docker.com/docker-for-mac/release-notes/#docker-community-edition-17120-ce-mac45-2018-01-05-edge){: target="_blank" class="_"}
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or higher.
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> - [Kubernetes on Docker for Windows](https://docs.docker.com/docker-for-windows/kubernetes/){: target="_blank" class="_"}
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is available in
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[18.02.0-ce Edge](https://docs.docker.com/docker-for-windows/release-notes/#docker-community-edition-18020-ce-rc1-win50-2018-01-26-edge){: target="_blank" class="_"}
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or higher.
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Virtual machines run guest operating systems—note the OS layer in each
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box. This is resource intensive, and the resulting disk image and application
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state is an entanglement of OS settings, system-installed dependencies, OS
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security patches, and other easy-to-lose, hard-to-replicate ephemera.
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### Container diagram
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Containers can share a single kernel, and the only information that needs to be
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in a container image is the executable and its package dependencies, which never
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need to be installed on the host system. These processes run like native
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processes, and you can manage them individually by running commands like `docker
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ps`—just like you would run `ps` on Linux to see active processes.
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Finally, because they contain all their dependencies, there is no configuration
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entanglement; a containerized app "runs anywhere."
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## Setup
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Before we get started, make sure your system has the latest version of Docker
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installed.
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[Install Docker](/install/index.md){: class="button outline-btn"}
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[Install Docker](/engine/installation/index.md){: class="button outline-btn"}
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<div style="clear:left"></div>
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> **Note**: version 1.13 or higher is required
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When you run `docker run hello-world`, look for a response like this:
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> **Note**: You may need to add your user to the `docker` group to call this command without sudo. [Read more](https://docs.docker.com/install/linux/linux-postinstall/)
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### Test Docker version
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> **Note**: If there are networking issues in your setup, `docker run hello-world` may fail to execute successfully. In case you are behind a proxy server and you suspect that it blocks the connection, check the [next part](/get-started/part2/) of the tutorial.
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Ensure that you have a supported version of Docker:
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```shell
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$ docker --version
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Docker version 17.12.0-ce, build c97c6d6
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```
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Run `docker version`(without `--`) or `docker info` to view even more details
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about your docker installation:
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```shell
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$ docker info
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Containers: 0
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Running: 0
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Paused: 0
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Stopped: 0
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Images: 0
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Server Version: 17.12.0-ce
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Storage Driver: overlay2
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...
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```
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> **Note**: To avoid permission errors (and the use of `sudo`), add your user to
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> the `docker` group. [Read more](https://docs.docker.com/engine/installation/linux/linux-postinstall/){: target="_blank" class="_"}.
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### Test Docker installation
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Test that your installation works by running the simple Docker image,
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[hello-world](https://hub.docker.com/_/hello-world/){: target="_blank" class="_"}:
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```shell
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$ docker run hello-world
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Unable to find image 'hello-world:latest' locally
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latest: Pulling from library/hello-world
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ca4f61b1923c: Pull complete
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Digest: sha256:ca0eeb6fb05351dfc8759c20733c91def84cb8007aa89a5bf606bc8b315b9fc7
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Status: Downloaded newer image for hello-world:latest
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Hello from Docker!
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This message shows that your installation appears to be working correctly.
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To generate this message, Docker took the following steps:
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...(snipped)...
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...
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```
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Now would also be a good time to make sure you are using version 1.13 or higher. Run `docker --version` to check it out.
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List the `hello-world` image that was downloaded to your machine:
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```shell
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$ docker --version
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Docker version 17.05.0-ce-rc1, build 2878a85
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$ docker image ls
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```
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If you see messages like the ones above, you are ready to begin your journey.
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List the `hello-world` container (spawned by the image), which exits after
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displaying its message. If it were still running, you would _not_ need the
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`--all` option:
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## Conclusion
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```shell
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$ docker container ls --all
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CONTAINER ID IMAGE COMMAND CREATED STATUS
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54f4984ed6a8 hello-world "/hello" 20 seconds ago Exited (0) 19 seconds ago
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```
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The unit of scale being an individual, portable executable has vast
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implications. It means CI/CD can push updates to any part of a distributed
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application, system dependencies are not an issue, and resource density is
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increased. Orchestration of scaling behavior is a matter of spinning up new
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executables, not new VM hosts.
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## Recap and cheat sheet
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This tutorial discusses all of these things, but first let's start with the
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basics.
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```shell
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## List Docker CLI commands
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docker
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docker container --help
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## Display Docker version and info
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docker --version
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docker version
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docker info
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## Excecute Docker image
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docker run hello-world
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## List Docker images
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docker image ls
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## List Docker containers (running, all, all in quiet mode)
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docker container ls
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docker container ls -all
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docker container ls -a -q
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```
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## Conclusion of part one
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Containerization makes [CI/CD](https://www.docker.com/use-cases/cicd){: target="_blank" class="_"} seamless. For example:
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- applications have no system dependencies
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- updates can be pushed to any part of a distributed application
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- resource density can be optimized.
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With Docker, scaling your application is a matter of spinning up new
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executables, not running heavy VM hosts.
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[On to Part 2 >>](part2.md){: class="button outline-btn" style="margin-bottom: 30px; margin-right: 100%"}
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