diff --git a/nixops/nixops.nix b/nixops/nixops.nix
index 617f7e5..561a1da 100644
--- a/nixops/nixops.nix
+++ b/nixops/nixops.nix
@@ -9,7 +9,6 @@
   rpi-2 = import ./rpi.nix { host = "rpi-2"; rpi4 = false; experimental-users = true; };
   rpi-3 = import ./rpi.nix { host = "rpi-3"; rpi4 = true; };
   rpi-4 = import ./rpi.nix { host = "rpi-4"; rpi4 = true; };
-  rpi-ext = import ./rpi-server.nix { host = "rpi-ext"; rpi4 = true; };
   zeus = import ./desktop.nix { host = "zeus"; };
   hera = import ./desktop.nix { host = "hera"; };
   hestia = import ./desktop.nix { host = "hestia"; };
diff --git a/nixops/rpi-server.nix b/nixops/rpi-server.nix
deleted file mode 100644
index 6505419..0000000
--- a/nixops/rpi-server.nix
+++ /dev/null
@@ -1,122 +0,0 @@
-{ host, rpi4 }:
-
-{ config, pkgs, ... }:
-{
-  deployment.targetHost = host;
-  deployment.hasFastConnection = true;
-  nix.nixPath = [ "nixpkgs=${pkgs.path}" ];
-  programs.command-not-found.dbPath = "${pkgs.path}/programs.sqlite";
-  nixpkgs.system = "aarch64-linux";
-
-  boot.loader.grub.enable = false;
-  boot.loader.generic-extlinux-compatible.enable = true;
-  boot.kernelParams = ["cma=64M"]; # work around https://github.com/raspberrypi/linux/issues/3208
-  boot.kernelPackages = pkgs.linuxPackages_rpi4;
-  boot.initrd.includeDefaultModules = false;
-
-  fileSystems = {
-    "/" = {
-      device = "/dev/disk/by-label/NIXOS_SD";
-      fsType = "ext4";
-    };
-  };
-
-  services.openssh.enable = true;
-  services.openssh.passwordAuthentication = false;
-  services.openssh.extraConfig =
-    ''
-    StreamLocalBindUnlink yes
-    '';
-  programs.mosh.enable = true;
-
-  networking.hostName = host;
-  time.timeZone = "Asia/Hong_Kong";
-
-  hardware.enableRedistributableFirmware = true;
-  services.hostapd = {
-    enable        = true;
-    interface     = "wlan0";
-    hwMode        = "g";
-    ssid          = "M-Labs-ext";
-    wpaPassphrase = (import /etc/nixos/secret/wifi_ext_password.nix);
-    extraConfig   = ''
-      ieee80211d=1
-      country_code=HK
-      ieee80211n=1
-      wmm_enabled=1
-      auth_algs=1
-      wpa_key_mgmt=WPA-PSK
-      rsn_pairwise=CCMP
-    '';
-  };
-  networking.interfaces.eth0 = {
-    ipv4.addresses = [{
-      address = "192.168.1.30";
-      prefixLength = 24;
-    }];
-    ipv6.addresses = [{
-      address = "2001:470:f821:1:dea6:32ff:fe95:2fcf";
-      prefixLength = 64;
-    }];
-    ipv4.routes = [{
-      address = "0.0.0.0";
-      prefixLength = 0;
-      via = "192.168.1.1";
-    }];
-    ipv6.routes = [{
-      address = "::";
-      prefixLength = 0;
-      via = "fe80::523e:aaff:fe0c:e49d";
-    }];
-  };
-  networking.interfaces.wlan0 = {
-    ipv4.addresses = [{
-      address = "192.168.13.1";
-      prefixLength = 24;
-    }];
-    ipv6.addresses = [{
-      address = "2001:470:f821:3::";
-      prefixLength = 64;
-    }];
-  };
-  services.dnsmasq = {
-    enable = true;
-    servers = ["192.168.1.1#53"];
-    extraConfig = ''
-      interface=wlan0
-      bind-interfaces
-      dhcp-range=192.168.13.10,192.168.13.254,24h
-      enable-ra
-      dhcp-range=::,constructor:wlan0,ra-only
-      no-resolv
-    '';
-  };
-  boot.kernel.sysctl."net.ipv4.ip_forward" = 1;
-  boot.kernel.sysctl."net.ipv6.conf.all.forwarding" = "1";
-  boot.kernel.sysctl."net.ipv6.conf.default.forwarding" = "1";
-
-  users.extraGroups.plugdev = { };
-  users.mutableUsers = false;
-  users.defaultUserShell = pkgs.fish;
-  users.extraUsers = import ./common-users.nix { inherit pkgs; };
-  security.sudo.wheelNeedsPassword = false;
-  services.udev.extraRules = (import ./extra-udev.nix);
-
-  documentation.enable = false;
-  environment.systemPackages = with pkgs; [
-    psmisc wget vim git sshfs usbutils lm_sensors file mosh tmux
-    imagemagick
-  ];
-  programs.fish.enable = true;
-
-  networking.firewall.allowedTCPPorts = [ 631 ];
-  networking.firewall.interfaces.wlan0.allowedUDPPorts = [ 53 67 ];
-
-  nix.settings.trusted-public-keys = ["nixbld.m-labs.hk-1:5aSRVA5b320xbNvu30tqxVPXpld73bhtOeH6uAjRyHc="];
-  nix.settings.substituters = ["https://nixbld.m-labs.hk" "https://cache.nixos.org"];
-  nix.settings.trusted-users = ["root" "sb"];
-
-  nix.extraOptions = ''
-    experimental-features = nix-command flakes impure-derivations
-  '';
-}