nixos-nspawn [WIP]

Fast and simple way to create a systemd-nspawn container from a flake.

Benefits

• Host and Container share a nix store, thereby improving performance and size.
• Standalone container don't require system rebuilds on change

Usage

• Install & Start: sudo install-container [containername] starts a container in the shell. If no entry for containername is found at /var/lib/machines/ a new container is created instead. machinectl may be used on running containers, but needs extra configuration to be able to start the container.
• Update: Updating the config can be done from within the container. Rerunning the install-container-script also works but needs the container to be shut down.
• Destroy: sudo destroy-container [containername] stops and removes the container as well as its entries in /nix/var/nix/profiles and /nix/var/nix/gcroots

Configuration

• Edit the install-container-script to fit your needs.
• Add the following to your nixos config to use machinectl to start the container:

{ pkgs, ... }:

let containerName = "template";
in
{
  systemd.nspawn."${containerName}" = {
    execConfig = {
      Boot = false;
      Parameters = "/nix/var/nix/profiles/system/init";
    };
    filesConfig = {
      BindReadOnly = [
        "/nix/store"
        "/nix/var/nix/db"
        "/nix/var/nix/daemon-socket"
      ];
      Bind = [
        "/nix/var/nix/profiles/per-container/${containerName}:/nix/var/nix/profiles"
        "/nix/var/nix/gcroots/per-container/${containerName}:/nix/var/nix/gcroots"
      ];
    };
    networkConfig = {
        Private = true;
    };
  };
}

Note

This is not the most "Nix-way" to deploy containers but helpful for testing.