How to add Cockpit UI for virtual machines to NixOS

Nov 22, 2023

Introduction

Cockpit is a cutting-edge web-based graphical interface for server management. It allows you to administer servers effortlessly and includes a built-in terminal.

Personally, I utilize the NixOS package to monitor system logs, network settings, services, system resources, and CPU load and all without needing to touch the command line.

With the Cockpit UI for virtual machines, you can create, run, and manage virtual machines directly in your browser. Since Cockpit runs within NixOS, I thought it would be interesting to test its virtual machines UI. My aim was to replace Proxmox with NixOS, and then it would be useful to be able to create virtual machines. However, I eventually paused my testing and decided to further explore Quickemu along with Quickgui.

Caution

Please note that the following is not a working setup. I am simply sharing my findings and the progress I’ve made so far. You’ll need to conduct further testing yourself to get it fully functional. If you manage to get it working (creating a VM), I’d love to hear about it in the comments!

Note

Ultimately, I replaced Proxmox with XCP-ng.

How To

Unfortunately, Cockpit machines is not available as a package. However there was an outdated package within the Nix User Repository (NUR), so I decided to add a custom package declaratively.

1. First create the packages/cockpit directory

   Run the following command:

   Linux

   # Open your terminal application
   sudo mkdir -p  /etc/nixos/packages/cockpit

2. Create /etc/nixos/packages/cockpit/default.nix

   Linux

   /etc/nixos/packages/cockpit/default.nix

     # To edit use your text editor application, for example Nano
     { pkgs, ... }:
   
     {
       virtual-machines = pkgs.callPackage ./virtual-machines.nix { };
       # podman-containers = pkgs.callPackage ./podman-containers.nix { };
     }

   You can add podman-containers.nix in the same way, but we will ignore that for now.

3. Create /etc/nixos/packages/cockpit/virtual-machines.nix

   Linux

   /etc/nixos/packages/cockpit/virtual-machines.nix

     # To edit use your text editor application, for example Nano
     { lib, stdenv, fetchzip, gettext }:
   
     stdenv.mkDerivation rec {
       pname = "cockpit-machines";
       version = "302";
   
       src = fetchzip {
         url = "https://github.com/cockpit-project/cockpit-machines/releases/download/${version}/cockpit-machines-${version}.tar.xz";
         sha256 = "sha256-3dfB9RzFzN578djOSdANVcb0AZ0vpSq6lIG7uMwzAVU=";
       };
   
       nativeBuildInputs = [
         gettext
       ];
   
       makeFlags = [ "DESTDIR=$(out)" "PREFIX=" ];
   
       postPatch = ''
         substituteInPlace Makefile \
           --replace /usr/share $out/share
         touch pkg/lib/cockpit.js
         touch pkg/lib/cockpit-po-plugin.js
         touch dist/manifest.json
       '';
   
       postFixup = ''
         gunzip $out/share/cockpit/machines/index.js.gz
         sed -i "s#/usr/bin/python3#/usr/bin/env python3#ig" $out/share/cockpit/machines/index.js
         sed -i "s#/usr/bin/pwscore#/usr/bin/env pwscore#ig" $out/share/cockpit/machines/index.js
         gzip -9 $out/share/cockpit/machines/index.js
       '';
   
       dontBuild = true;
   
       meta = with lib; {
         description = "Cockpit UI for virtual machines";
         license = licenses.lgpl21;
         homepage = "https://github.com/cockpit-project/cockpit-machines";
         platforms = platforms.linux;
         maintainers = with maintainers; [ ];
       };
     }

   The above is inspired by this script. Adjust the version if necessary.

   Tip

   If it is not easy to determine the shaS256 of the tar.gz file, then switch to the new NixOS configuration with the wrong value, the new sha256 will then be mentioned.

4. Add the cockpit-apps to configuration.nix

   Linux

   /etc/nixos/configuration.nix

     # To edit use your text editor application, for example Nano
     { config, pkgs, lib, ... }:
   
     let
       cockpit-apps = pkgs.callPackage packages/cockpit/default.nix { inherit pkgs; };
     in
     {
       imports =
       [ # Include the results of the hardware scan.
         ./hardware-configuration.nix
       ];
   
       environment.systemPackages = with pkgs; [
         cockpit
         # cockpit-apps.podman-containers
         cockpit-apps.virtual-machines
         libvirt # Needed for virtual-machines
         virt-manager # Needed for virtual-machines
       ];
   
     # Add the rest of the configuration here
   
     }

   According to some sources it may be necessary to add libvirtd or qemu-libvirtd to the user’s extraGroups, but I have not tested that further.

   Note

   In this case I am using the Cockpit, libvirt and virt-manager packages from the default channel. But you can also use a newer version from the unstable channel (if available).

5. Switch NixOS configuration

   Now you can switch to the new NixOS configuration. Run the following command:

   Linux

   # Open your terminal application
   sudo nix-collect-garbage # Optional: clean up
   sudo nixos-rebuild switch

6. Check the results

   Now you can browse to Cockpit and the virtual machines UI by opening a web browser and going to: http://localhost:9090. Replace localhost with the relevant IP address or FQDN if needed, and adjust the port if you changed it earlier.

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Tags:

• Virtualisation
• Linux

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