NixOS stuff

Uprading and cleaning up

To upgrade nixos, run nixos-rebuild as normal, but with the --upgrade switch

$ sudo nixos-rebuild switch --upgrade

Running nixos-rebuild switch causes system generations start to build up. This increases the length of the grub menu and these generations will cause the nix store to hang on to a bunch of older versions of packages. To list these generations, use nix-env with the profile switch

$ sudo nix-env --list-generations --profile /nix/var/nix/profiles/system

To remove generations, use the nix-collect-garbage command as root, something like this

$ sudo nix-collect-garbage --delete-older-than 14d

which will delete all generations older that 14 days. You can then use the nix-env command from above to see the shortened list.

Deploying Printers in CUPS

It's really easy to deploy printers on nixos. I make a printers.nix file specifically with printers settings and then include it in the main configuration.nix file. This way you can just not include the printers in configurations that don't need them, like servers.

{ config, lib, pkgs, modulesPath, ... }:

{
    environment.systemPackages = with pkgs; [
        hplip
    ];
    services.printing.enable = true;
    services.printing.drivers = [ pkgs.hplip ];
    hardware.printers  = {
        ensurePrinters = [
        {
            name = "Home80-LaserJet";
            description = "HP Color LaserJet M254dw";
            deviceUri = "ipp://192.168.0.122/";
            #model = "drv:///sample.drv/generpcl.ppd";
            #model = "drv:///sample.drv/laserjet.ppd";
            model = "HP/hp-color_laserjet_pro_m252-ps.ppd.gz";
        }
        ];
    };
}

sudo with no password for wheel group

Disabling the password requirement for sudo is easy. This example shows how to do it for the wheel group. This can be pasted directly into configuration.nix. It's probably not a good idea.

  security.sudo.extraRules= [
    {  groups = [ "wheel" ];
      commands = [
         { command = "ALL" ;
           options= [ "NOPASSWD" ]; # "SETENV" # Adding the following could be a good idea
        }
      ];
    }
  ];

Great video explaining NixOS and more

Ampersand on youtube make a greate video explaining all aspects of nix.