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+## directory structure
+- by-name/<hostname>: configuration which is evaluated _only_ for the given hostname
+- common/: configuration which applies to all hosts
+- modules/: nixpkgs-style modules which may be used by multiple hosts, but configured separately per host.
+    - ideally no module here has effect unless `enable`d
+        - however, `enable` may default to true
+        - and in practice some of these modules surely aren't fully "disableable"