How to get Nix-OS running in Unraid

This guide walks through setting up a NixOS virtual machine in Unraid from scratch. The goal is a minimal, declarative server that you can use as a base for self-hosted services. We’ll cover creating the VM, partitioning the disk, installing NixOS with a sensible server configuration, and getting SSH access working.

NixOS uses a single configuration file to define the entire system — packages, users, services, networking. This means the setup is reproducible and can be version-controlled. Instead of running commands to install packages and edit config files across the system, everything lives in configuration.nix.

This guide is a simplified walkthrough based on the official NixOS installation manual, combined for x86_64, UEFI, and Unraid. Refer to the official docs for edge cases or alternative setups.

1. Download the NixOS minimal ISO

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This guide uses the x86_64 image. NixOS also provides an aarch64 (ARM64) build, but the steps below are written for x86_64.

Grab the minimal ISO image for x86_64 from the NixOS download page. Choose the latest minimal installer image and place the .iso file in your Unraid ISO share (typically /mnt/user/isos/).

2. Set up the Unraid VM

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Create a new VM in Unraid using the Linux template. I used the following settings but feel free to adjust them to your needs:

This guide assumes a UEFI boot setup. The VM must use OVMF firmware — a BIOS/SeaBIOS VM will not work with the partition layout and boot loader configuration below.

3. Partition the disk

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Boot the VM from the ISO. You’ll be logged in as the nixos user — switch to root with sudo -i.

parted /dev/vda -- mklabel gpt
parted /dev/vda -- mkpart ESP fat32 1MB 512MB
parted /dev/vda -- set 1 esp on
parted /dev/vda -- mkpart root ext4 512MB 100%

Check:

lsblk

You should see roughly:

vda
├─vda1   511M
└─vda2   <rest of disk>

4. Format the partitions

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mkfs.fat -F 32 -n BOOT /dev/vda1
mkfs.ext4 -L nixos /dev/vda2

No swap partition — for a self-hosted server the RAM allocation is predictable, so swap is rarely needed. You can always add a swap file later if a service requires it.

5. Mount the root filesystem

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mount /dev/disk/by-label/nixos /mnt

We use the disk label (nixos) instead of /dev/vda2 so the mount survives disk order changes.

6. Mount the EFI partition

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mkdir -p /mnt/boot
mount -o umask=077 /dev/disk/by-label/BOOT /mnt/boot

You can verify:

lsblk -o NAME,SIZE,FSTYPE,LABEL,MOUNTPOINTS

You should see:

vda
├─vda1  vfat  BOOT   /mnt/boot
└─vda2  ext4  nixos  /mnt

7. Generate the NixOS configuration

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nixos-generate-config --root /mnt

This auto-detects your hardware and creates two files:

/mnt/etc/nixos/configuration.nix       # main config — you edit this
/mnt/etc/nixos/hardware-configuration.nix  # auto-generated — leave as-is

8. Edit the configuration

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nano /mnt/etc/nixos/configuration.nix

Replace the entire file with this minimal but solid starting point for a VPS server:

{ config, pkgs, ... }:

{
  imports = [
    ./hardware-configuration.nix
  ];

  boot.loader.systemd-boot.enable = true;
  boot.loader.efi.canTouchEfiVariables = true;

  # Use latest kernel.
  boot.kernelPackages = pkgs.linuxPackages_latest;

  networking.hostName = "nixos";

  # NetworkManager is for desktops — disabled on a static server
  networking.networkmanager.enable = false;
  # Check the interface name with `ip link` before editing
  networking.interfaces.enp1s0.useDHCP = true;

  time.timeZone = "Europe/Berlin";

  i18n.defaultLocale = "en_US.UTF-8";

  users.users.flohoss = {
    isNormalUser = true;
    description = "Florian Hoss";
    # wheel group grants sudo privileges
    extraGroups = [ "wheel" ];
  };

  services.openssh.enable = true;

  networking.firewall.enable = true;
  networking.firewall.allowedTCPPorts = [ 22 ];

  environment.systemPackages = with pkgs; [
    vim
    wget
  ];

  system.stateVersion = "26.05"; # Update this to match your NixOS version
}

Replace the username and hostname with your own values. The interface name (enp1s0) may differ — check it with ip link before editing.

9. Install NixOS

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Once your configuration is ready:

nixos-install --root /mnt

It will ask you to set/confirm the root password. Once the install finishes, you can unmount:

umount /mnt/boot /mnt

10. Reboot

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reboot

Then remove/disable the NixOS installer ISO in Unraid so the VM boots from /dev/vda.

After reboot, open the Unraid VNC console and set a password for your user:

passwd flohoss

You can now log in via SSH with the password:

ssh flohoss@<vm-ip>

Upload your SSH key so you can log in without a password:

ssh-copy-id -i ~/.ssh/id_ed25519.pub flohoss@<vm-ip>

11. Harden SSH

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Now that your key is in place, disable password and root login. Edit the configuration on the VM:

sudo nano /etc/nixos/configuration.nix

Add the following inside the existing services.openssh block:

  services.openssh = {
    enable = true;
    settings = {
      PermitRootLogin = "no";
      PasswordAuthentication = false;
    };
  };

Rebuild and switch:

sudo nixos-rebuild switch

Why not put the key in the config? The key you uploaded with ssh-copy-id lives in ~/.ssh/authorized_keys in your home directory, which nixos-rebuild never touches — it only manages the system in the Nix store. So the key survives every rebuild. It would only be lost on a full disk wipe/reinstall.

You might be tempted to declare the key directly in configuration.nix via openssh.authorizedKeys.keys — the NixOS way. But the initial config is edited in the Unraid VNC console (step 8), where copy-paste is flaky at best (especially from macOS) — typing an entire SSH public key by hand is impractical. ssh-copy-id over SSH after the first boot is the reliable approach. You can always move the key into the config later for a fully declarative setup — by then you’re editing over SSH where paste works.

From now on you can only log in with your key — no passwords accepted over SSH. You’ll use the same sudo nixos-rebuild switch command after any future config change.