diff --git a/nixbld-etc-nixos/configuration.nix b/nixbld-etc-nixos/configuration.nix
index e2bdb7e..9d556d3 100644
--- a/nixbld-etc-nixos/configuration.nix
+++ b/nixbld-etc-nixos/configuration.nix
@@ -289,21 +289,7 @@ in
 
   nix.distributedBuilds = true;
   nix.nrBuildUsers = 64;
-  nix.buildMachines = [
-    {
-       hostName = "localhost";
-       maxJobs = 10;
-       system = "x86_64-linux";
-       supportedFeatures = ["big-parallel"];
-    }
-    {
-       hostName = "rpi-3";
-       sshUser = "nix";
-       sshKey = "/etc/nixos/secret/nix_id_rsa";
-       maxJobs = 1;
-       system = "aarch64-linux";
-    }
-  ];
+  nix.trustedUsers = ["sb"];
   services.hydra = {
     enable = true;
     package = pkgs.hydra-unstable;
diff --git a/nixbld-etc-nixos/secret_permissions.txt b/nixbld-etc-nixos/secret_permissions.txt
index 14c7dd7..d9094b5 100644
--- a/nixbld-etc-nixos/secret_permissions.txt
+++ b/nixbld-etc-nixos/secret_permissions.txt
@@ -7,6 +7,5 @@
 -rw------- 1 uwsgi        uwsgi          mattermost-github-integration.py
 -rw------- 1 nginx        nginx          muninpasswd
 -rw-rw---- 1 hydra        hydra          nixbld.m-labs.hk-1
--rw-rw---- 1 hydra        hydra          nix_id_rsa
 -rw------- 1 root         root           wifi_password.nix
 -rw------- 1 sb           users          wifi_ext_password.nix