sys/fs: add single layout assertion

1 files changed, 7 insertions, 0 deletions

diff --git a/sys/fs/layout.nix b/sys/fs/layout.nix
index 999492d..897cffe 100644
--- a/sys/fs/layout.nix
+++ b/sys/fs/layout.nix
@@ -73,5 +73,12 @@ in {
       layoutOpts = [ layout.sysHddBtrfs ];
       valid = filter ({ snd, ... }: snd != null) (zipLists layoutMaps layoutOpts);
     in optionalAttrs (valid != []) ((head valid).fst (head valid).snd);
+
+    assertions = [
+      {
+        assertion = length (filter (layout: layout != null) (attrValues cfg.fs.layout)) <= 1;
+        message = "Cannot enable more than one filesystem layout";
+      }
+    ];
   };
 }