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 `Open in Browser` in the notification telling you: `Your service running on port 3000 is available`.
- Clicking the globe icon in the 'Ports' view. The 'Ports' view gives you an organized table of your forwarded ports, and you can access it with the command **Ports: Focus on Ports View**.
- Notice port 3000 in the 'Ports' view is labeled "Hello Remote World." In `devcontainer.json`, you can set `"portsAttributes"`, such as a label for your forwarded ports and the action to be taken when the port is autoforwarded.
> **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 notification 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.
- Press <kbd>F1</kbd> and select the **Remote-Containers: Rebuild Container** or **Codespaces: Rebuild Container** command so the modifications are picked up.
