diff --git a/morph/README.rst b/morph/README.rst
index d008f07bd7c514da4d6808acf5a503087e03dfa5..33062489c50a1d364a1f249ed8e8a5af755b56d9 100644
--- a/morph/README.rst
+++ b/morph/README.rst
@@ -7,6 +7,13 @@ and some JSON-based configuration in ``.config.json`` files.
 
 This configuration is fed to `morph`_ to make changes to the deployment.
 
+bootstrap-configuration.nix
+---------------------------
+
+This is meant as a minimal system configuration to use as part of crossgrading a Debian install to NixOS.
+It has a lot of comments explaining different parts of Nix and NixOS.
+You may want to browse it before looking at other ``.nix`` files here.
+
 grid.config.json
 ----------------
 
@@ -23,4 +30,23 @@ You can do things like build the network::
 
   morph build grid.nix
 
+<hostname>-hardware.nix
+-----------------------
+
+These are the generated hardware-related configuration files for servers in the grid.
+These files are referenced from the corresponding ``<hostname>.nix`` files.
+
+<hostname>-config.nix
+---------------------
+
+Each such file contains a minimal Nix expression supplying critical system configuration details.
+"Critical" roughly corresponds to anything which must be specified to have a bootable system.
+These files are referenced by the corresponding ``<hostname>.nix`` files.
+
+<hostname>.nix
+--------------
+
+Each such file contains the parts of the system configuration that aren't *so* related to hardware.
+They are referenced from ``grid.nix``.
+
 .. _`morph`: https://github.com/DBCDK/morph
diff --git a/morph/staging002.nix b/morph/staging002.nix
index 443c127d55b1bbea82078f60167798b639d1f1f8..df0f2e9a04846c8b85f515ca07bce8745f26de92 100644
--- a/morph/staging002.nix
+++ b/morph/staging002.nix
@@ -1,12 +1,18 @@
-{ config, pkgs, ... }:
-{ imports =
+{ ... }:
+{
+  imports =
     [ # Include the results of the hardware scan.
       ./staging002-hardware.nix
       # Configure it as a system operated by 100TB.
-      # Instance details are read from <hostName>.config.json
       ../nixos/modules/100tb.nix
     ];
 
+  # Pass the configuration specific to this host to the 100TB module to be
+  # expanded into a complete system configuration.  See the 100tb module for
+  # handling of this value.
+  #
+  # The module name is quoted because `1` makes `100tb` look an awful lot like
+  # it should be a number.
   "100tb".config = import ./staging002-config.nix;
 
   # This value determines the NixOS release with which your system is to be
diff --git a/nixos/modules/100tb.nix b/nixos/modules/100tb.nix
index c701acd7001545809146ca97cad50e10d82d3862..243da0dd72913ed4f582b52ca5cfe0494936c744 100644
--- a/nixos/modules/100tb.nix
+++ b/nixos/modules/100tb.nix
@@ -1,7 +1,36 @@
-# A NixOS module which configures a system that is hosted by 100TB.
-{ pkgs, lib, config, ... }:
+# A NixOS module which configures a system that is hosted by 100TB.  Each of
+# our servers hosted with 100TB will probably import this module and pass it
+# the minimum system configuration to get the server to boot and accept
+# administrative ssh connections.
+#
+# A NixOS module is defined as a Nix expression language function.
+{
+  # This contains generally useful library functionality provided by nixpkgs.
+  # These are things like string manipulation and, notably for us, a library
+  # for defining options for configuring moduless.
+  lib,
+
+  # This is all of the configuration for a particular system where this module
+  # might be instantiated.  For any system where we want the 100TB module to
+  # be active, this should have the 100TB configuration details (IP, gateway,
+  # etc).
+  config,
+
+  # More parameters exist and are accepted but we don't need them so we ignore them.
+  ...
+}:
 let
+  # Pull out the configuration for this module for convenient use later.  The
+  # module name is quoted because `1` makes `100tb` look an awful lot like it
+  # should be a number.
   cfg = config."100tb".config;
+
+  # Define the API to this module.  Everything in `options` is about
+  # specifying what kind of values we expect to be given.  This is both
+  # human-facing documentation as well as guidance to NixOS about acceptable
+  # values (mainly by type) so it can automatically reject certain bogus
+  # values.  This value is in the `let` to make the code below a little easier
+  # to read.  See below where we use it.
   options = {
     interface = lib.mkOption
     { type = lib.types.str;
@@ -42,6 +71,9 @@ let
     };
   };
 in {
+  # Here we actually define the module's options.  They're what we said they
+  # were above, all bundled up into a "submodule" which is really just a set
+  # of options.
   options =
   { "100tb".config = lib.mkOption
     { type = lib.types.submodule { inherit options; };
@@ -49,16 +81,31 @@ in {
     };
   };
 
+  # Now compute the configuration that results from whatever values were
+  # supplied for our options.  A lot of this is currently very similar to
+  # what's in bootstrap-configuration.nix (which is well commented).  The
+  # similarity makes sense - both that configuration and this one need to get
+  # a 100TB machine to boot and let an admin SSH in.
+  #
+  # Values that go into `config` here are merged into values that go into
+  # `config` in any other active modules.  Basically, everything in this
+  # `config` is treated as if it were in the configuration set defined by
+  # `/etc/nixos/configuration.nix`.  The module just gives us a way to factor
+  # separate concerns separately and make reuse easier.
+  #
+  # Note that this is not where Tahoe-LAFS configuration goes.  It's just
+  # about getting base platform into good shape.
+  #
+  # Perhaps at some point this can be refactored to remove the duplication.
+  # It's slightly tricky because we don't want to introduce any external
+  # dependencies to bootstrap-configuration.nix because that would make it
+  # harder to deploy in the bootstrap environment.
   config =
   { boot.loader.grub.enable = true;
     boot.loader.grub.version = 2;
     boot.loader.grub.device = "/dev/disk/by-id/${cfg.grubDeviceID}";
 
-    # Get a slightly faster boot time than default.  Maybe this could even be
-    # 0 but I'm not sure.
     boot.loader.timeout = 1;
-
-    # Let me in to do subsequent configuration.
     networking.firewall.enable = false;
     services.openssh.enable = true;
 
@@ -66,7 +113,6 @@ in {
       cfg.rootPublicKey
     ];
 
-    # Provide the static network configuration.
     networking.dhcpcd.enable = false;
     networking.interfaces = {
       "${cfg.interface}".ipv4.addresses = [