shadow: add shellPath passthru

This one is a bit special, it's used to deny users from logging in.

pkgs/os-specific/linux/shadow/default.nix

@@ -53,5 +53,8 @@ stdenv.mkDerivation rec {
   meta = {
     homepage = http://pkg-shadow.alioth.debian.org/;
     description = "Suite containing authentication-related tools such as passwd and su";
+    passthru = {
+      shellPath = "/bin/nologin";
+    };
   };
 }

pkgs/top-level/all-packages.nix

@@ -2233,6 +2233,9 @@ in
   else
     nodePackages_4_x;
 
+  # Can be used as a user shell
+  nologin = shadow;
+
   npm2nix = nodePackages.npm2nix;
 
   ldapvi = callPackage ../tools/misc/ldapvi { };