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NixOS Coder templates for AWS EC2
Get started with Linux development on AWS EC2.
cloud
aws
nix
nixos
flakes
arm
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NixOS Coder templates for AWS

A simple set of templates that allows you to use a NixOS flake to configure a Coder workspace.

See here for more information about distributing a NixOS configuration via a flake.

What templates are provided?

This contains 4 templates, driven by the YAML files under the values/ directory:

  • aws-nixos: NixOS on AWS x86 instances.
  • aws-nixos-spot: NixOS on AWS x86 spot instances.
  • aws-nixos-graviton: Nixos on AWS Graviton (aarch64) instances.
  • aws-nixos-graviton-spot: Nixos on AWS Graviton (aarch64) spot instances.

How do I set this up?

  • To create all templates: ./push-all.sh create
  • To push all templates: ./push-all.sh
  • To push an individual template: coder templates push -d . --variables-file ./values/VALUES_FILE.yaml TEMPLATE_NAME

Some notes before using this yourself

Using the home disk

Because your NixOS config defines the entire system, it must define mounting the /home device. The backing block device is hard-coded to be available at /dev/xvdb.

You can accomplish this with the following:

fileSystems."/home" = {
  device = "/dev/xvdb";
  fsType = "ext4";  # Or another filesystem, if you prefer
  autoFormat = true;
}

Authentication

This currently depends on your desired flake being publicly available, and requiring no secrets to build.

One could feasibly remove this limitation by granting the created instance an IAM role that could fetch items from AWS Secret Manager, and adding logic to the setup script to fetch these secrets and put them in the right place.

I haven't implemented any functionality for this, mostly because it's not relevant to me right now, but I would consider accepting PRs that implement this in a relatively generic way.

Startup time

There may be a short gap (2-3m) between the time the instance finishes provisioning and the time Nix logs start being streamed to the UI. This is expected, the time is spent applying a minimal bootstrap configuration that allows the Coder agent to start as the configured non-root user.

This allows logs from nixos-rebuild to be viewed in the UI, as well as allowing SSH into the instance in case the run of nixos-rebuild fails.

Debugging

If your NixOS configuration fails to apply for whatever reason, the agent will still be able to drop you into a shell for your given user. Logs for the initial configuration are streamed, and viewable in the UI/CLI.

Username

The agent user is configurable as a workspace parameter, because people can set arbitrary usernames in their NixOS configuration. The default username is configured as denbeigh, because that's the username I use. To change the default username, set the default_agent_user variable when pushing these templates.

The username given must correspond to a username created in your NixOS configuration.