NixOS Vagrant Plugin

This plugin makes working with NixOS guests in Vagrant a bit nicer:

• Allow network configurations
• Allow hostname setting
• Provide nix provisioning

Install:

$ vagrant plugin install vagrant-nixos

Example Vagrantfile

Vagrant.configure("2") do |config|

	# use a suitable NixOS base
	# http://github.com/oxdi/nixos
	config.vm.box = "nixos-14.02-x86_64"
	config.vm.box_url = "http://s3.amazonaws.com/oxdi/nixos-14.02-x86_64-virtualbox.box"
  	
  	# set hostname
  	config.vm.hostname = "nixy"
  
  	# Setup networking
	config.vm.network "private_network", :ip => "172.16.16.16"

	# Add the htop package
	config.vm.provision :nixos, :expression => {
		environment: {
			systemPackages: [ :htop ]
		}
	}

end

In the above Vagrantfile example we provision the box using the :expression method, which will perform a simple ruby -> nix conversion. :expression provisioning creates a nix module that executes with pkgs in scope. It is roughly equivilent to the below version that uses the :inline method.

config.vm.provision :nixos, :inline => %{
	{config, pkgs, ...}: with pkgs; {
		environment.systemPackages = [ htop ];
	}
}, :NIX_PATH => "/custom/path/to/nixpkgs"

The above example also shows the optional setting of a custom NIX_PATH path.

You can also use an external nix configuration file:

config.vm.provision :nixos, :path => “configuration.nix”

If you need provisioning to be included explicitly during rebuild use:

config.vm.provision :nixos,
	:path => “configuration.nix”,
	:include => true

You can enable verbose provision output during rebuild process with:

config.vm.provision :nixos,
	:path => “configuration.nix”,
	:verbose => true

If you need to use functions or access values using dot syntax you can use the Nix module:

config.vm.provision :nixos, :expression => {
	services: {
		postgresql: {
			enable: true,
			package: Nix.pkgs.postgresql93,
			enableTCPIP: true,
			authentication: Nix.lib.mkForce(%{
				local all all              trust
				host  all all 127.0.0.1/32 trust
			}),
			initialScript: "/etc/nixos/postgres.sql"
		}
	}
}	

How it works

In nixos we don't mess around with the files in /etc instead we write expressions for the system configuration starting in /etc/nixos/configuration.nix.

This plugin sets some ground rules for nixos boxes to keep this configuration clean and provisioning possible.

Box creators should ensure that their configuration.nix file imports an nix module /etc/nixos/vagrant.nix which will be overwritten by vagrant-nixos during vagrant up or vagrant provision.

See the configuration in our NixOS packer template for an example.

Issues

It's a bit slow on the initial boot/provision at the moment as it must run nixos-rebuild several times. This is far from ideal I'm sure I'll find a better place to hook in the rebuild step soon.