NixOS as a Proxmox LXC

It should be straightforward to setup NixOS on a Proxmox LXC, right? Well, apparently not.

For starters, the latest Proxmox documentation here flat out didn’t work for me but the out of date one here did after a few tweaks. Here are the steps I took for my future self.

Step 1

Get one of the latest, and appropriate, container builds from here and upload to Proxmox as an LXC template.

Step 2

Create a new container through PVE shell:

pct create $(pvesh get /cluster/nextid) \
  --arch amd64 \
  local:vztmpl/nixos-system-x86_64-linux.tar.xz \
  --ostype unmanaged \
  --net0 name=eth0,bridge=vmbr0,firewall=1,tag=20 \
  --storage local-lvm \
  --unprivileged 1 \
  --features nesting=1 \
  --cmode console \
  --onboot 1

For me, even when I set static IP through Proxmox, the container ignored that and used DHCP. So, I plan to fix that through Nix configuration later.

Step 3

Fix resource configuration (for e.g., memory, disk space etc.) through Proxmox UI, if required, start the container, run the following inside it and reboot:

nix-channel --update

Step 5

Hold on, you aren’t done yet. While you can access the container through the console, you still can’t SSH into it.

Set a root password by:

passwd

Add the following by doing a nano /etc/nixos/configuration.nix. (This is, of course, insecure. Do it temporarily, just to get SSH from personal machine working, and then update.)

  services.openssh = {
    enable = true;
    settings.PasswordAuthentication = true;
    settings.PermitRootLogin = "yes";
  };

And then:

nixos-rebuild switch

Finally, do an ifconfig to find the IP address and then SSH with:

ssh root@IP