unstablePkgs should allow unfree

flake.nix

@@ -16,7 +16,7 @@
     let
       system = "x86_64-linux";
       pkgs = nixpkgs.legacyPackages.${system};
-      unstablePkgs = unstable.legacyPackages.${system};
+      unstablePkgs = import unstable { inherit system; config.allowUnfree = true; };
       updatePkgs = import update { inherit system; config.allowUnfree = true; };
     in {
       nixosConfigurations = {
@@ -43,6 +43,7 @@
           system = "x86_64-linux";
           specialArgs = { inherit unstablePkgs updatePkgs nixos-hardware; };
           modules = [
+            { nixpkgs.overlays = [ (import ./overlays/zfs-replicate.nix) ]; }
             ./hosts/axl/configuration.nix
             home-manager.nixosModules.home-manager
             {

overlays/zfs-replicate-env-fix.patch

@@ -0,0 +1,11 @@
+--- a/zfs/replicate/filesystem/list.py
++++ b/zfs/replicate/filesystem/list.py
+@@ -42,4 +42,4 @@ def list(  # pylint: disable=W0622
+ def _list(filesystem: FileSystem) -> str:
+     options = ["-H", "-o name,readonly", "-t filesystem,volume", "-r"]
+
+-    return f"/usr/bin/env - zfs list {' '.join(options)} '{filesystem.name}'"
++    return f"/usr/bin/env zfs list {' '.join(options)} '{filesystem.name}'"
+
+
+ def _filesystems(zfs_list_output: bytes) -> List[FileSystem]:

overlays/zfs-replicate.nix

@@ -0,0 +1,7 @@
+final: prev: {
+  zfs-replicate = prev.zfs-replicate.overrideAttrs (oldAttrs: {
+    patches = (oldAttrs.patches or []) ++ [
+      ./zfs-replicate-env-fix.patch
+    ];
+  });
+}