diff --git a/nix/system/configuration.nix b/nix/system/configuration.nix
index e661513..a95f096 100644
--- a/nix/system/configuration.nix
+++ b/nix/system/configuration.nix
@@ -66,9 +66,11 @@
   networking.firewall = {
     allowedTCPPorts = [
       631 # CUPs port for printing
+      4000 # phoenix development port
     ];
     allowedUDPPorts = [
       631
+      4000
     ];
   };
   # Or disable the firewall altogether.
@@ -80,6 +82,9 @@
   # programs.mtr.enable = true;
   programs.gnupg.agent = { enable = true; enableSSHSupport = true; };
 
+  # enable ADB for connecting to android phones
+  programs.adb.enable = true;
+
   # List services that you want to enable:
 
   # Enable fingerprint reading
@@ -140,6 +145,7 @@
     extraGroups = [
       "wheel" # Enable ‘sudo’ for the user.
       "networkmanager" # Allow the user to manage networks
+      "adbusers" # allow ADB use
     ];
   };
 
@@ -154,7 +160,10 @@
   # servers. You should change this only after NixOS release notes say you
   # should.
   system.stateVersion = "21.05"; # Did you read the comment?
-  system.autoUpgrade.enable = true;
+
+  # On 2021-12-01 or thereabouts, a new generation was created that failed to
+  # boot; that's a little worrying!
+  system.autoUpgrade.enable = false;
 }