74 lines
3.4 KiB
Markdown
74 lines
3.4 KiB
Markdown
---
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next_page: app.md
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---
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## The command you just ran
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Congratulations! You have started the container for this tutorial!
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Let's first explain the command that you just ran. In case you forgot,
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here's the command:
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```cli
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docker run -d -p 80:80 docker/getting-started
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```
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You'll notice a few flags being used. Here's some more info on them:
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- `-d` - run the container in detached mode (in the background)
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- `-p 80:80` - map port 80 of the host to port 80 in the container
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- `docker/getting-started` - the image to use
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!!! info "Pro tip"
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You can combine single character flags to shorten the full command.
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As an example, the command above could be written as:
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```
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docker run -dp 80:80 docker/getting-started
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```
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## The Docker Dashboard
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Before going too far, we want to highlight the Docker Dashboard, which gives
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you a quick view of the containers running on your machine. It gives you quick
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access to container logs, lets you get a shell inside the container, and lets you
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easily manage container lifecycle (stop, remove, etc.).
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To access the dashboard, follow the instructions for either
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[Mac](https://docs.docker.com/docker-for-mac/dashboard/) or
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[Windows](https://docs.docker.com/docker-for-windows/dashboard/). If you open the dashboard
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now, you will see this tutorial running! The container name (`jolly_bouman` below) is a
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randomly created name. So, you'll most likely have a different name.
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## What is a container?
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Now that you've run a container, what _is_ a container? Simply put, a container is
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simply another process on your machine that has been isolated from all other processes
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on the host machine. That isolation leverages [kernel namespaces and cgroups](https://medium.com/@saschagrunert/demystifying-containers-part-i-kernel-space-2c53d6979504), features that have been
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in Linux for a long time. Docker has worked to make these capabilities approachable and easy to use.
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!!! info "Creating Containers from Scratch"
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If you'd like to see how containers are built from scratch, Liz Rice from Aqua Security
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has a fantastic talk in which she creates a container from scratch in Go. While she makes
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a simple container, this talk doesn't go into networking, using images for the filesystem,
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and more. But, it gives a _fantastic_ deep dive into how things are working.
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<iframe width="560" height="315" src="https://www.youtube-nocookie.com/embed/8fi7uSYlOdc" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>
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## What is a container image?
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When running a container, it uses an isolated filesystem. This custom filesystem is provided
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by a **container image**. Since the image contains the container's filesystem, it must contain everything
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needed to run an application - all dependencies, configuration, scripts, binaries, etc. The
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image also contains other configuration for the container, such as environment variables,
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a default command to run, and other metadata.
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We'll dive deeper into images later on, covering topics such as layering, best practices, and more.
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!!! info
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If you're familiar with `chroot`, think of a container as an extended version of `chroot`. The
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filesystem is simply coming from the image. But, a container adds additional isolation not
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available when simply using chroot.
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