README.md

@@ -0,0 +1,103 @@
+# GNU Guix System Explorer
+
+“What’s this?”, you ask.  It’s a hack, initially written for [a FOSDEM
+2021 talk](https://fosdem.org/2021/schedule/event/gnuguix/), that allows
+you to navigate the
+[services](https://guix.gnu.org/manual/en/html_node/Services.html) of
+your [Guix System](https://guix.gnu.org)
+[configuration](https://guix.gnu.org/manual/en/html_node/Using-the-Configuration-System.html)
+and the connections among them.
+
+## Exploring your system
+
+It’s very bare-bones, my friend!  Assuming the Guix modules are in your
+`GUILE_LOAD_PATH`—it’s the case on Guix System—you can run, say:
+
+```sh
+./explore.scm /run/current-system/configuration.scm
+```
+
+That spawns a web server on port 8080, which you can talk to from your
+browser by `http://localhost:8080`.  And what do you see there?
+
+![Animation of showing interaction with the Guix System Explorer.](demo.gif)
+
+Voilà!
+
+## What is this showing?
+
+If you’ve tried [`guix system
+extension-graph`](https://guix.gnu.org/manual/en/html_node/Invoking-guix-system.html)
+before, it is showing something similar.  On the graph displayed, each
+node represents a _service_ of your system configuration, and each edge
+represents a _service extension_.  Essential services are shown as red
+circles, [“base”
+services](https://guix.gnu.org/manual/en/html_node/Base-Services.html#index-_0025base_002dservices-1)
+are represented as smaller red circles, and user services are smaller
+gray circles.  When **hovering over a service**, its documentation is
+displayed at the top left.
+
+When **clicking on a service**, its _value_ gets displayed.  For example,
+the value of the `udev` service is a record containing (1) the (e)udev
+package it uses, and (2) the set of udev rules.  For the `openssh`
+service, the value is [a record listing the various `sshd`
+options](https://guix.gnu.org/manual/en/html_node/Networking-Services.html#index-openssh_002dconfiguration).
+
+The graph shows, for example, an arrow from the `openssh` to the
+`accounts` service, which is responsible for setting up user accounts.
+When **clicking on this arrow**, we see the “value” that `openssh`
+_contributes_ to `accounts`: it’s a list consisting of the `sshd` group
+and the `sshd` user account—the “privilege separation” account used by
+`sshd`.
+
+Last, when **double-clicking on a service**, you can see the effect of
+[_folding_ all the services that contribute to
+it](https://guix.gnu.org/manual/en/html_node/Service-Reference.html#index-fold_002dservices).
+For example, when double-clicking on `shepherd-root`, all the services
+with an incoming edge contribute a value to this service—a Shepherd
+service—and are no longer displayed.  At this point, clicking on
+`shepherd-root` shows its new value: a list of [`shepherd-service`
+records](https://guix.gnu.org/manual/en/html_node/Shepherd-Services.html#index-shepherd_002dservice).
+
+Ultimately, all services can be folded into
+[`system`](https://guix.gnu.org/manual/en/html_node/Service-Reference.html#index-system_002dservice_002dtype),
+which the the “root” of all services, representing the final, assembled
+operating system.
+
+## Why?
+
+Modern GNU/Linux distributions are complex beasts and it’s hard to get
+the big picture.  This tool aims to help users answer questions such as:
+What components make up my system?  How are they composed together?  How
+does the high-level configuration of a service translate into the
+configuration of lower-level services?
+
+Ultimately, I would like to think of this tool not just as a helper for
+Guix System users, but also as an educational tool—a tool to help users
+and enthusiast learn how things are glued together.  It’s about
+empowering users, reducing the gap between “those who know” and “those
+who use”.
+
+## What’s next?
+
+Who knows what’s next!  There are certainly glitches here and there in
+the user interface that could be fixed, and convenience features that
+could be added.  Perhaps this tool could be made part of Guix proper, as
+a new `guix system explore` sub-command?
+
+So far the tool is only about exploring the system.  What if we allowed
+users to _edit_ their system configuration right from the user
+interface?  Food for thought!
+
+## Join us!
+
+Things you can do:
+
+  - Watch the accompanying FOSDEM 2021 talk, [_Declaratively
+    Yours—Composing system abstractions with
+    GNU Guix_](https://fosdem.org/2021/schedule/event/gnuguix/).
+  - Try it yourself, and [hack
+    it](https://notabug.org/civodul/guix-explorer)!
+  - [Get in touch with Guix!](https://guix.gnu.org/en/contact/)
+  
+Ludovic Courtès, February 2021.

explore.scm

@@ -551,10 +551,7 @@ latest changes."
          (thread-state (not-found request) view store)))
       (thread-state (not-found request) view store)))
 
-(use-modules (gnu tests))
-
-(define* (run-explore-server #:optional (os (simple-operating-system))
-                             #:key (port 8080))
+(define* (run-explore-server os #:key (port 8080))
   (define user-services
     (operating-system-user-services os))