From dc87f8e0809d2c4453b8f6460e33a879af098574 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <eelco.dolstra@logicblox.com>
Date: Mon, 18 Nov 2013 16:26:39 +0100
Subject: [PATCH] Check whether fileSystems defines the root FS

---
 nixos/modules/system/boot/stage-1.nix | 5 +++++
 nixos/modules/tasks/filesystems.nix   | 1 +
 2 files changed, 6 insertions(+)

diff --git a/nixos/modules/system/boot/stage-1.nix b/nixos/modules/system/boot/stage-1.nix
index b2b66280372..7f7184b1e45 100644
--- a/nixos/modules/system/boot/stage-1.nix
+++ b/nixos/modules/system/boot/stage-1.nix
@@ -330,6 +330,11 @@ in
 
   config = {
 
+    assertions = singleton
+      { assertion = any (fs: fs.mountPoint == "/") (attrValues config.fileSystems);
+        message = "The ‘fileSystems’ option does not specify your root file system.";
+      };
+
     system.build.bootStage1 = bootStage1;
     system.build.initialRamdisk = initialRamdisk;
     system.build.extraUtils = extraUtils;
diff --git a/nixos/modules/tasks/filesystems.nix b/nixos/modules/tasks/filesystems.nix
index 3f484045ed4..b0bcd2eb373 100644
--- a/nixos/modules/tasks/filesystems.nix
+++ b/nixos/modules/tasks/filesystems.nix
@@ -81,6 +81,7 @@ in
   options = {
 
     fileSystems = mkOption {
+      default = {};
       example = {
         "/".device = "/dev/hda1";
         "/data" = {