Unified nixPath

hosts/airgead.nix

@@ -15,9 +15,5 @@
 
   networking.hostName = "airgead";   # Define your hostname.
 
-  nix.nixPath = [
-    "nixpkgs=https://nixos.org/channels/nixos-20.03/nixexprs.tar.xz"
-  ];
-
   system.stateVersion = "20.03";   # The version of NixOS originally installed
 }

hosts/cuallaidh.nix

@@ -25,9 +25,5 @@
 
   networking.hostName = "cuallaidh";   # Define your hostname.
 
-  nix.nixPath = [
-    "nixpkgs=https://nixos.org/channels/nixos-20.03/nixexprs.tar.xz"
-  ];
-
   system.stateVersion = "19.03";   # The version of NixOS originally installed
 }

hosts/iolear-beag.nix

@@ -17,22 +17,6 @@
   deployment.targetHost = "10.69.0.158";
   networking.hostName = "iolear-beag";   # Define your hostname.
 
-  # Adapted from gchristensen
-  nix.nixPath = [
-    # Ruin the config so we don't accidentally run
-    # nixos-rebuild switch on the host
-    (let
-      cfg = pkgs.writeText "configuration.nix"
-        ''
-          assert builtins.trace "This system is managed by NixOps." false;
-          {}
-        '';
-    in "nixos-config=${cfg}")
-
-    # Copy the channel version from the deploy host to the target
-    "nixpkgs=https://nixos.org/channels/nixos-20.03/nixexprs.tar.xz"
-  ];
-
   system.stateVersion = "18.09";   # The version of NixOS originally installed
 
 }

hosts/paidh-ceithir.nix

@@ -14,9 +14,5 @@
   environment.systemPackages = with pkgs; [
   ];
 
-  nix.nixPath = [
-    "nixpkgs=https://nixos.org/channels/nixos-20.03/nixexprs.tar.xz"
-  ];
-
   system.stateVersion = "19.09";       # The version of NixOS originally installed
 }

hosts/paidh-coig.nix

@@ -14,9 +14,5 @@
   environment.systemPackages = with pkgs; [
   ];
 
-  nix.nixPath = [
-    "nixpkgs=https://nixos.org/channels/nixos-20.03/nixexprs.tar.xz"
-  ];
-
   system.stateVersion = "19.09";       # The version of NixOS originally installed
 }

hosts/paidh-tri.nix

@@ -17,9 +17,5 @@
     nixops                # NixOS cloud provisioning and deployment tool
   ];
 
-  nix.nixPath = [
-    "nixpkgs=https://nixos.org/channels/nixos-20.03/nixexprs.tar.xz"
-  ];
-
   system.stateVersion = "19.09";       # The version of NixOS originally installed
 }

hosts/sithlainnir.nix

@@ -17,22 +17,6 @@
   deployment.targetHost = "10.69.0.121";
   networking.hostName = "sithlainnir";   # Define your hostname.
 
-  # Adapted from gchristensen
-  nix.nixPath = [
-    # Ruin the config so we don't accidentally run
-    # nixos-rebuild switch on the host
-    (let
-      cfg = pkgs.writeText "configuration.nix"
-        ''
-          assert builtins.trace "This system is managed by NixOps." false;
-          {}
-        '';
-    in "nixos-config=${cfg}")
-
-    # Copy the channel version from the deploy host to the target
-    "nixpkgs=https://nixos.org/channels/nixos-20.03/nixexprs.tar.xz"
-  ];
-
   system.stateVersion = "18.09";   # The version of NixOS originally installed
 
 }

hosts/teintidh.nix

@@ -19,10 +19,6 @@
   deployment.targetHost = "10.69.0.141";
   networking.hostName = "teintidh";   # Define your hostname.
 
-  nix.nixPath = [
-    "nixpkgs=https://nixos.org/channels/nixos-20.03/nixexprs.tar.xz"
-  ];
-
   system.stateVersion = "18.09";   # The version of NixOS originally installed
 
 }

roles/host_common.nix

@@ -37,11 +37,34 @@
     powerline-fonts   # Required for Powerline prompts
   ];
 
-  # Enable Nix garbage collection:
+  # Adapted from gchristensen and clever
-  nix.gc.automatic = true;
+  nix = {
-  nix.gc.dates = "weekly";
+    nixPath = [
-  nix.gc.options = "--delete-older-than 90d";
+      # Ruin the config so we don't accidentally run
-  nix.autoOptimiseStore = true;
+      # nixos-rebuild switch on the host
+      (let
+        cfg = pkgs.writeText "configuration.nix"
+          ''
+            assert builtins.trace "This system is managed by NixOps." false;
+            {}
+          '';
+      in "nixos-config=${cfg}")
+
+      # Copy the channel version from the deploy host to the target
+      "nixpkgs=/run/current-system/nixpkgs"
+    ];
+    gc = {
+      automatic = true;   # Enable Nix garbage collection:
+      dates = "weekly";
+      options = "--delete-older-than 90d";
+    };
+    autoOptimiseStore = true;
+  };
+
+  system.extraSystemBuilderCmds = ''
+    ln -sv ${pkgs.path} $out/nixpkgs
+  '';
+  environment.etc.host-nix-channel.source = pkgs.path;
 
   # Set the system-wide environment
   environment = {