Making a home NAS using NixOS

Still playing with NixOS, I wanted to experience how difficult it would be to write a NixOS configuration file to turn a computer into a simple NAS with basics features: samba storage, dlna server and auto suspend/resume.

What is NixOS? As a reminder for some and introduction to the others, NixOS is a Linux distribution built by the Nix package manager, which make it very different than any other operating system out there, except Guix which has a similar approach with their own package manager written in Scheme.

NixOS uses a declarative configuration approach along with lot of others features derived from Nix. What’s big here is you no longer tweak anything in /etc or install packages, you can define the working state of the system in one configuration file. This system is a totally different beast than the others OS and require some time to understand how it work. Good news though, everything is documented in the man page configuration.nix, from fstab configuration to users managements or how to enable samba!

Here is the /etc/nixos/configuration.nix file on my NAS.

It enables ssh server, samba, minidlna and vnstat. Set up a user with my ssh public key. Ready to work.

Using rtcwake command (Linux specific), it’s possible to put the system into standby mode and schedule an auto resume after some time. This is triggered by a cron job at 01h00.

{ config, pkgs, ... }:
{
  # include stuff related to hardware, auto generated at install
  imports = [ ./hardware-configuration.nix ];
  boot.loader.grub.device = "/dev/sda";
      
  # network configuration
  networking.interfaces.enp3s0.ipv4.addresses = [ {
    address = "192.168.42.150";
    prefixLength = 24;
  } ];
  networking.defaultGateway = "192.168.42.1";
  networking.nameservers = [ "192.168.42.231" ];
      
  # FR locales and layout
  i18n.defaultLocale = "fr_FR.UTF-8";
  console = { font = "Lat2-Terminus16"; keyMap = "fr"; };
  time.timeZone = "Europe/Paris";
      
  # Packages management
  environment.systemPackages = with pkgs; [
    kakoune vnstat borgbackup utillinux
  ];
      
  # network disabled (I need to check the ports used first)
  networking.firewall.enable = false;
      
  # services to enable
  services.openssh.enable = true;
  services.vnstat.enable = true;
      
  # auto standby
  services.cron.systemCronJobs = [
      "0 1 * * * root rtcwake -m mem --date +6h"
  ]; 
      
  # samba service
  services.samba.enable = true;
  services.samba.enableNmbd = true;
  services.samba.extraConfig = ''
        workgroup = WORKGROUP
        server string = Samba Server
        server role = standalone server
        log file = /var/log/samba/smbd.%m
        max log size = 50
        dns proxy = no
        map to guest = Bad User
    '';
  services.samba.shares = {
      public = {
          path = "/home/public";
          browseable = "yes";
          "writable" = "yes";
          "guest ok" = "yes";
          "public" = "yes";
          "force user" = "share";
        };
     };
      
  # minidlna service
  services.minidlna.enable = true;
  services.minidlna.announceInterval = 60;
  services.minidlna.friendlyName = "Rorqual";
  services.minidlna.mediaDirs = ["A,/home/public/Musique/" "V,/home/public/Videos/"];
      
  # trick to create a directory with proper ownership
  # note that tmpfiles are not necesserarly temporary if you don't
  # set an expire time. Trick given on irc by someone I forgot the name..
  systemd.tmpfiles.rules = [ "d /home/public 0755 share users" ];
      
  # create my user, with sudo right and my public ssh key
  users.users.solene = {
    isNormalUser = true;
    extraGroups = [ "wheel" "sudo" ];
    openssh.authorizedKeys.keys = [
          "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIOIZKLFQXVM15viQXHYRjGqE4LLfvETMkjjgSz0mzMzS personal"
          "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIOIZKLFQXVM15vAQXBYRjGqE6L1fvETMkjjgSz0mxMzS pro"
    ];
  };
      
  # create a dedicated user for the shares
  # I prefer a dedicated one than "nobody"
  # can't log into it
  users.users.share= {
    isNormalUser = false;
  };
}