This article will walk you through the process of running NixOS in a QEMU virtual machine (VM) on a Linux host system. Basic nix configuration to help with connectivity to the VM from the host is also included.

This article assumes you’re on a Arch Linux host system. Instructions may vary with regards to package installation on other distros, but the rest of the steps should be largely identical. Additionally, your machine must support virtualization and have it enabled in the BIOS/UEFI settings.

Installing QEMU and QEMU Utilities

You’ll need the QEMU emulator package for your host architecture along with the qemu-img utility to create disk images. On Arch Linux, you can install these packages in a single command:

sudo pacman -S qemu-full

Verify the installation by running:

qemu-system-x86_64 --version
qemu-img --version

Tip: qemu-full is a large package that includes support for multiple architectures. If you want to save space, you can install only the emulator for your host architecture (for example, qemu-system-x86_64 for x86_64 hosts). If you go this route, remember to additionally install the qemu-img package.

Downloading the NixOS ISO

You can download the latest NixOS ISO from the NixOS download page. For a first time user, it’s best to download a “Graphical ISO image”. Graphical installation ISOs contain a desktop environment with an installation wizard.

Installing NixOS to a Virtual Disk

Create a disk image for your NixOS VM. The following command creates a 30GB QCOW2 image.

qemu-img create -f qcow2 nixos-vm.qcow2 30G

The base installation comfortably fits within 10GB. That said, give yourself at least another 20GB for app installs.

Create a bash script in the same directory as your QCOW2 image called start-nixos-vm.sh. Add the following content to boot the NixOS installation ISO:

#!/bin/bash

qemu-system-x86_64 \
    -m 6144 \
    -smp 3 \
    -drive file=nixos-vm.qcow2,format=qcow2 \
    -cdrom /path/to/nixos-graphical-25.11.941.c97c47f2bac4-x86_64-linux.iso \
    -boot d \
    -net nic \
    -net user,hostfwd=tcp::2222-:22 \
    -enable-kvm

You may want to adjust the following parameters based on your system and preferences:

Run the start-nixos-vm.sh script to boot into the installation ISO. The install wizard should launch automatically. Follow the on-screen instructions to complete the installation. Once done, shut down the VM.

Booting into NixOS

Modify the start-nixos-vm.sh script to boot from the virtual disk instead of the installation ISO. Update the script as follows:

#!/usr/bin/env bash

qemu-system-x86_64 \
    -m 6144 \
    -smp 3 \
    -drive file=nixos.qcow2,format=qcow2 \
    -net nic \
    -net user,hostfwd=tcp::2222-:22 \
    -enable-kvm

Remember to adjust the -m and -smp values as needed.

Running the script once more should boot you into your newly installed NixOS VM. From here, you can begin your NixOS journey from the comfort of a virtual machine.

Bonus: SSH Access

With the -net user,hostfwd=tcp::2222-:22 option in the QEMU command, you can SSH into your NixOS VM from the host machine. But first, you’ll need to enable SSH in your configuration.nix. Follow these steps to connect via SSH:

1. Run your NixOS VM.
2. Edit your nix config:

sudo nano /etc/nixos/configuration.nix`.

3. Uncomment or add the line services.openssh.enable = true;.
4. Rebuild your NixOS configuration:

sudo nixos-rebuild switch`.

5. On the host machine, run the following command replacing <USERNAME> with your NixOS username:

ssh -p 2222 <USERNAME>@localhost