Proxmox Virtual Environment

Proxmox Virtual Environment - shortened PVE - (wikipedia:en:Proxmox Virtual Environment) is a platform for containerization and virtualization. PVE can manage a so called "data center" as a cluster of machines and storage. (It supports file systems like ZFS and Ceph.) Mostly it can be used with a WUI. It is open source and is based on Debian GNU/Linux (with a customized kernel of Ubuntu).

Proxmox VE uses

• #KVM for virtualization and
• #LXC for containerization.

NixOS runs on both.

The instructions should work for PVE 7.2 and later with NixOS 22.05 and later.

KVM

It is possible to generate generic qcow2 images and attach them to VMs with qm importdisk as shown here.

A better option is to generate a VMA image that can be imported as a VM on Proxmox VE. With this method, many VM configuration options such as CPU, memory, network interfaces, and serial terminals can be specified in nix instead of manually setting them on the Proxmox UI.

Generating VMA

The first run will take some time, as a patched version of qemu with support for the VMA format needs to be built

nix run github:nix-community/nixos-generators -- --format proxmox

Pass additional nix configuration to the template with --configuration filename.nix. In addition to NixOS module options, Proxmox-specific options present in nixos/modules/virtualisation/proxmox-image.nix can be used to set core, memory, disk and other VM hardware options.

Deploying on Proxmox VE

The generated vma.zst file can be copied to /var/lib/vz/dump/ (or any other configured VM dump storage path). A new VM can be spun up from it either using the GUI or the CLI:

qmrestore /var/lib/vz/dump/vzdump-qemu-nixos-21.11.git.d41882c7b98M.vma.zst <vmid> --unique true

note: the MAC address of net0 defaults to 00:00:00:00:00:00. This must either be overridden through proxmox.qemuConf.net0, or the unique attribute must be set to true when importing the image on Proxmox VE.

By default, the generated image is set up to expose a serial terminal interface for ease of access.

root@proxmox-server:~# qm start <vmid>
root@proxmox-server:~# qm terminal <vmid>
starting serial terminal on interface serial0 (press Ctrl+O to exit)

<<< NixOS Stage 1 >>>

loading module dm_mod...
running udev...
Starting version 249.4
.
.
.
[  OK  ] Reached target Multi-User System.


<<< Welcome to NixOS 21.11.git.d41882c7b98M (x86_64) - ttyS0 >>>

Run 'nixos-help' for the NixOS manual.

nixos login: root (automatic login)


[root@nixos:~]#

Network configuration

Cloud-init can be enabled with

services.cloud-init.network.enable = true;

This will enable systemd-networkd, allowing cloud-init to set up network interfaces on boot.

LXC

Generating LXC template

Classic NixOS Channels:

nix run --extra-experimental-features nix-command --extra-experimental-features flakes github:nix-community/nixos-generators -- --format proxmox-lxc

NixOS Flakes and Nix-Command Enabled:

nix run github:nix-community/nixos-generators -- --format proxmox-lxc

Privileged LXCs

While it’s not necessary, proxmoxLXC.privileged can be set to true to enable the DebugFS mount in privileged LXCs. If enabled on unprivileged LXCs, this will fail to mount.

Network configuration

The Proxmox LXC template uses systemd-networkd by default to allow network configuration by Proxmox. proxmoxLXC.manageNetwork can be set to true to disable this.

Deploying on Proxmox VE

Copy the tarball to Proxmox VE, then create a new LXC with this template through the web UI or the CLI. The “nesting” feature needs to be enabled. Newer versions of Proxmox VE will have it enabled by default.

As of now, not all of the configuration options on the web UI work for Proxmox LXCs. Network configuration and adding SSH keys to root user work, while setting a password for the root user and setting hostname don’t.

It is suggested to set a root password within the container on first boot.

The template built above without any options does not come with /etc/nixos/configuration.nix. A minimal working example is presented below. Be sure to run nix-channel --update, reboot the container running before nixos-rebuild switch.

{ pkgs, modulesPath, ... }:

{
  imports = [
    (modulesPath + "/virtualisation/proxmox-lxc.nix")
  ];

  environment.systemPackages = [
    pkgs.vim
  ];
}

Note: As of December 2024, the nixos-generators template for Proxmox LXC has a limitation: nixos-rebuild does not apply changes to the container, despite appearing successful. To add packages or make changes, create a new CT template with the desired configuration pre-applied.

LXC Console

You may need to set the Console Mode option to /dev/console (instead of the default of "tty") in order to make the console shell work.

Note: Disregard this for NixOS 24.05 or newer. The LXC Console is fixed by the NixOS team.

LXC See also

• earlier wiki page Proxmox Linux Container

Name

Proxmox Virtual Environment is also called

short Proxmox VE,

shortened PVE,

just Proxmox.

Proxmox is the firm of the company Proxmox Server Solutions GmbH. Besides Proxmox Virtual Environment (PVE) there are other products called Proxmox Backup Server (PBS) and Proxmox Mail Gateway (PMG).