Dev Containers tutorial

This tutorial walks you through running Visual Studio Code in a Docker container using the Dev Containers extension. You need no prior knowledge of Docker to complete this tutorial.

Running VS Code inside a Docker container can be useful for many reasons, but in this walkthrough we'll focus on using a Docker container to set up a development environment that is separate from your local environment.

Prerequisites

You need Visual Studio Code installed.

Install Docker

Docker is needed to create and manage your containers.

Docker Desktop

Download and install Docker Desktop, or an alternative Docker option, like Docker on a remote host or Docker compliant CLI.

Start Docker

Run the Docker Desktop application to start Docker. You will know it's running if you look in the activity tray and see the Docker whale icon.

Docker might take a few minutes to start. If the whale icon is animated, it is probably still in the process of starting. You can click on the icon to see the status.

Check Docker

Once Docker is running, you can confirm that everything is working by opening a new terminal window and typing the command:

docker --version
# Docker version 18.09.2, build 6247962

Install the extension

The Dev Containers extension lets you run Visual Studio Code inside a Docker container.

Install the Dev Containers extension

Check installation

With the Dev Containers extension installed, you will see a new Status bar item at the far left.

The Remote Status bar item can quickly show you in which context VS Code is running (local or remote) and clicking on the item will bring up the Dev Containers commands.

Get the sample

To create a Docker container, we are going to open a GitHub repository with a Node.js project.

Open the Command Palette (F1) to run the command Dev Containers: Try a Dev Container Sample... and select the Node sample from the list.

Note: There are other dev container samples such as vscode-remote-try-python or vscode-remote-try-java, but this tutorial will use vscode-remote-try-node.

Wait for the container to build

The window will then reload, but since the container does not exist yet, VS Code will create one and clone the sample repository into an isolated container volume. This may take some time, and a progress notification will provide status updates. Fortunately, this step isn't necessary the next time you open the folder since the container will already exist.

After the container is built, VS Code automatically connects to it and maps the project folder from your local file system into the container.

Check the container

Once the container is running and you're connected, you should see your remote context change in the bottom left of the Status bar:

Check your environment

One of the useful things about developing in a container is that you can use specific versions of dependencies that your application needs without impacting your local development environment.

The specific container for this tutorial has Node.js v18 installed, which you can check by opening a new terminal Terminal > New Terminal (⌃⇧` (Windows, Linux Ctrl+Shift+`)) and entering:

node --version; npm --version

This should show the following versions:

Run the application

We can now hit F5, which will run the application inside the container. Once the process starts, navigate to http://localhost:3000 and you should see the simple Node.js server running!

Ending your container connection

You can end your session in the container and go back to running VS Code locally with File > Close Remote Connection.

How it works

This next section describes in more detail how the Dev Containers extension sets up and configures your containers.

The Dev Containers extension uses the files in the .devcontainer folder, namely devcontainer.json, and an optional Dockerfile or docker-compose.yml, to create your dev containers.

In the example we just explored, the project has a .devcontainer folder with a devcontainer.json inside. The devcontainer.json uses the image mcr.microsoft.com/devcontainers/javascript-node:0-18. You can explore this image in greater detail in the devcontainers/images repo.

First, your image is built from the supplied Dockerfile or image name, which would be mcr.microsoft.com/devcontainers/javascript-node:0-18 in this example. Then a container is created and started using some of the settings in the devcontainer.json. Finally your Visual Studio Code environment is installed and configured again according to settings in the devcontainer.json. For example, the dev container in this example installs the streetsidesoftware.code-spell-checker extension.

Note: Additional configuration will already be added to the container based on what's in the base image. For example, we see the streetsidesoftware.code-spell-checker extension above, and the container will also include "dbaeumer.vscode-eslint" as that's part of mcr.microsoft.com/devcontainers/typescript-node. This happens automatically when pre-building using devcontainer.json, which you may read more about in the pre-build section.

Once all of this is done, your local copy of Visual Studio Code connects to the Visual Studio Code Server running inside of your new dev container.

devcontainer.json

The devcontainer.json is basically a config file that determines how your dev container gets built and started.

//devcontainer.json
{
  "name": "Node.js",

  // Or use a Dockerfile or Docker Compose file. More info: https://containers.dev/guide/dockerfile
  "image": "mcr.microsoft.com/devcontainers/javascript-node:0-18",

  // Features to add to the dev container. More info: https://containers.dev/features.
  // "features": {},

  "customizations": {
    "vscode": {
      "settings": {},
      "extensions": ["streetsidesoftware.code-spell-checker"]
    }
  },

  // "forwardPorts": [3000],

  "portsAttributes": {
    "3000": {
      "label": "Hello Remote World",
      "onAutoForward": "notify"
    }
  },

  "postCreateCommand": "yarn install"

  // "remoteUser": "root"
}

The above example is extracted from the vscode-remote-try-node repo we used in the tutorial.

You can review the full list of devcontainer.json options.

Congratulations

Congratulations, you've successfully completed this tutorial!

This has been a brief overview of what is possible using dev containers. As a next step, we recommend checking out how you can open an existing folder from your machine in a container or opening a GitHub repository or PR in a container.

Check out the other Remote Development extensions.

• Remote - SSH
• WSL

Or get them all by installing the Remote Development Extension Pack.

Troubleshooting

Verify Docker context

If you are not using a fresh Docker install and the Dev Containers: Try a Dev Container Sample... sample encounters issues with the current context, you should check your Docker context. Fresh installs will have a 'default' context and you can set it back as the current context.

# Displays the list of contexts, '*' denotes the current context
docker context list

# Switches the list to the 'default' context
docker context use default