Replaced 'builtins.readFile' with 'lib.fileContents'.

config/nix.nix

@@ -1,4 +1,4 @@
-{ config, pkgs, ... }:
+{ config, lib, pkgs, ... }:
 
 {
   nix = {
@@ -9,7 +9,7 @@
     extraOptions = ''
       build-timeout = 86400  # 24 hours
     '';
-    binaryCachePublicKeys = [ (builtins.readFile /secret/hydra_cache.pub) ];
+    binaryCachePublicKeys = [ (lib.fileContents /secret/hydra_cache.pub) ];
     trustedBinaryCaches = [
       "https://cache.nixos.org"
       "https://cache.ophanim.de"

configuration.nix

@@ -2,9 +2,8 @@
 
 with lib;
 
-# hint: use 'echo -n' so there is no newline char in the hostName file
 let
-  machinePath = (builtins.toPath ("/etc/nixos/machines/" + (builtins.readFile /secret/hostName)));
+  machinePath = (builtins.toPath ("/etc/nixos/machines/" + (fileContents /secret/hostName)));
   machineConf = machinePath + "/configuration.nix";
   machineOpts = machinePath + "/options.nix";
 in {

services/mailserver.nix

@@ -9,7 +9,7 @@ mkIf (elem "mailserver" config.machine.services) {
     domains = [ config.machine.domain ];
     loginAccounts = {
         "derped@${config.machine.domain}" = {
-            hashedPassword = (builtins.readFile /secret/derped.mail);
+            hashedPassword = (fileContents /secret/derped.mail);
         };
     };
     # Use Let's Encrypt certificates. Note that this needs to set up a stripped

services/mariaDB.nix

@@ -3,7 +3,7 @@
 with lib;
 
 let
-  giteapwd = if config.services.gitea.enable then (builtins.readFile /secret/gitea) else "";
+  giteapwd = if config.services.gitea.enable then (fileContents /secret/gitea) else "";
 in mkIf (elem "mariaDB" config.machine.services) {
   services.mysql = {
     enable = true;