A **development container** is a running [Docker](https://www.docker.com) container with a well-defined tool/runtime stack and its prerequisites. You can try out development containers with **[GitHub Codespaces](https://github.com/features/codespaces)** or **[Visual Studio Code Remote - Containers](https://aka.ms/vscode-remote/containers)**.
This is a sample project that lets you try out either option in a few easy steps. We have a variety of other [vscode-remote-try-*](https://github.com/search?q=org%3Amicrosoft+vscode-remote-try-&type=Repositories) sample projects, too.
For more info, check out the [GitHub documentation](https://docs.github.com/en/free-pro-team@latest/github/developing-online-with-codespaces/creating-a-codespace#creating-a-codespace).
1. If this is your first time using a development container, please ensure your system meets the pre-reqs (i.e. have Docker installed) in the [getting started steps](https://aka.ms/vscode-remote/containers/getting-started).
> **Note:** Under the hood, this will use the **Remote-Containers: Clone Repository in Container Volume...** command to clone the source code in a Docker volume instead of the local filesystem. [Volumes](https://docs.docker.com/storage/volumes/) are the preferred mechanism for persisting container data.
> **Note:** This container runs as a non-root user with sudo access by default. Comment out `"remoteUser": "node"` in `.devcontainer/devcontainer.json` if you'd prefer to run as root.
- Try adding some code and check out the language features.
- Notice that `eslint` and the `vscode-eslint` extension are already installed in the container since the `.devcontainer/devcontainer.json` lists `"dbaeumer.vscode-eslint"` as an extension to install automatically when the container is created.
- Continue (<kbd>F5</kbd>). You can connect to the server in the container by either: clicking on `Running on http://0.0.0.0:3000` in the terminal output, or "Open in Browser" next to port 3000 in the 'Ports' view (you can get to the 'Ports' view by clicking on the "1" in the status bar, which means your app has 1 forwarded port).
> **Note:** In Remote - Containers, you can access your app at `http://localhost:3000` in a local browser. But in a browser-based Codespace, you must click the link from the terminal output or the `Ports` view so that the service handles port forwarding in the browser and generates the correct URL.
You may want to make changes to your container, such as installing a different version of a software or forwarding a new port. You'll rebuild your container for your changes to take effect.
> **Note:** Remote-Containers and Codespaces also take care of dynamic port forwarding, but there may be instances in which we want to statically declare a forwarded port.
