activationSripts: add previous var value (closes #6)

flake.nix

@@ -8,17 +8,20 @@
   outputs = { self, nixpkgs, not-os }:
     let
       pkgs = import nixpkgs { system = "x86_64-linux"; };
-      not-os-patches = [
+
+      patched-not-os = let
+        remote-patches = [
           {
             # Zynq image various fixes and cleanup
             url = "https://patch-diff.githubusercontent.com/raw/cleverca22/not-os/pull/28.patch";
             sha256 = "sha256-EnYb95QfwHmUHfbCT9tL291mC8Tze0Koadb11arvTDY=";
           }
         ];
-      patched-not-os = pkgs.applyPatches {
+        local-patches = [ ./not-os.patch ];
+      in pkgs.applyPatches {
         name = "not-os-patched";
         src = not-os;
-        patches = map pkgs.fetchpatch not-os-patches;
+        patches = map pkgs.fetchpatch remote-patches ++ local-patches;
       };
 
       gnu-platform = "arm-none-eabi";

not-os.patch

@@ -0,0 +1,28 @@
+diff --git a/base.nix b/base.nix
+index 7eaee32..b5a61ee 100644
+--- a/base.nix
++++ b/base.nix
+@@ -155,7 +155,23 @@ with lib;
+       # dummy to make setup-etc happy
+     '';
+     system.activationScripts.etc = stringAfter [ "users" "groups" ] config.system.build.etcActivationCommands;
++    # Re-apply deprecated var value due to systemd preference in recent nixpkgs
++    # See https://github.com/NixOS/nixpkgs/commit/59e37267556eb917146ca3110ab7c96905b9ffbd
++    system.activationScripts.var = lib.mkForce ''
++      # Various log/runtime directories.
+ 
++      mkdir -p /var/tmp
++      chmod 1777 /var/tmp
++
++      # Empty, immutable home directory of many system accounts.
++      mkdir -p /var/empty
++      # Make sure it's really empty
++      ${pkgs.e2fsprogs}/bin/chattr -f -i /var/empty || true
++      find /var/empty -mindepth 1 -delete
++      chmod 0555 /var/empty
++      chown root:root /var/empty
++      ${pkgs.e2fsprogs}/bin/chattr -f +i /var/empty || true
++    '';
+     # nix-build -A system.build.toplevel && du -h $(nix-store -qR result) --max=0 -BM|sort -n
+     system.build.toplevel = pkgs.runCommand "not-os" {
+       activationScript = config.system.activationScripts.script;