diff --git a/gui/README b/gui/README
new file mode 100644
index 00000000000..7eee9040e3f
--- /dev/null
+++ b/gui/README
@@ -0,0 +1,19 @@
+This file should become a nix expression.
+
+you need to:
+- download the latest jQuery from:
+    http://jqueryjs.googlecode.com/files/jquery-1.3.2.js
+    SHA1 Checksum: f0b95e99225f314fbe37ccf6b74ce2f916c517de
+
+- install 'xulrunner' with nix:
+    nix-env -i xulrunner
+
+- install and add nix-intantiate in your path
+
+- have /etc/nixos/nixpkgs
+- have /etc/nixos/nixos
+
+
+to run it, either:
+- cd /etc/nixos/nixos/gui; ./nixos-gui
+- xulrunner /etc/nixos/nixos/gui/application.ini
diff --git a/gui/application.ini b/gui/application.ini
new file mode 100644
index 00000000000..0da5e498dad
--- /dev/null
+++ b/gui/application.ini
@@ -0,0 +1,35 @@
+[App]
+;
+; This field specifies your organization's name.  This field is recommended,
+; but optional.
+Vendor=NixOS
+;
+; This field specifies your application's name.  This field is required.
+Name=NixOS-gui
+;
+; This field specifies your application's version.  This field is optional.
+Version=0.0
+;
+; This field specifies your application's build ID (timestamp).  This field is
+; required.
+BuildID=20090925
+;
+; This field specifies a compact copyright notice for your application.  This
+; field is optional.
+;Copyright=
+;
+; This ID is just an example.  Every XUL app ought to have it's own unique ID.
+; You can use the microsoft "guidgen" or "uuidgen" tools, or go on
+; irc.mozilla.org and /msg botbot uuid.  This field is optional.
+;ID=
+
+[Gecko]
+;
+; This field is required.  It specifies the minimum Gecko version that this
+; application requires.
+MinVersion=1.9a5
+;
+; This field is optional.  It specifies the maximum Gecko version that this
+; application requires.  It should be specified if your application uses
+; unfrozen interfaces.
+;MaxVersion=1.9.0.*
diff --git a/gui/chrome/chrome.manifest b/gui/chrome/chrome.manifest
new file mode 100644
index 00000000000..6b524807eaa
--- /dev/null
+++ b/gui/chrome/chrome.manifest
@@ -0,0 +1 @@
+content nixos-gui content/nixos-gui/
diff --git a/gui/chrome/content/nixos-gui/io.js b/gui/chrome/content/nixos-gui/io.js
new file mode 100644
index 00000000000..3e3b080b814
--- /dev/null
+++ b/gui/chrome/content/nixos-gui/io.js
@@ -0,0 +1,74 @@
+function makeTempFile(prefix)
+{
+  var file = Components.classes["@mozilla.org/file/directory_service;1"]
+                       .getService(Components.interfaces.nsIProperties)
+                       .get("TmpD", Components.interfaces.nsIFile);
+  file.append(prefix || "xulrunner");
+  file.createUnique(Components.interfaces.nsIFile.NORMAL_FILE_TYPE, 0664);
+  return file;
+}
+
+function writeToFile(file, data)
+{
+  // file is nsIFile, data is a string
+  var foStream = Components.classes["@mozilla.org/network/file-output-stream;1"]
+                           .createInstance(Components.interfaces.nsIFileOutputStream);
+
+  // use 0x02 | 0x10 to open file for appending.
+  foStream.init(file, 0x02 | 0x08 | 0x20, 0664, 0); // write, create, truncate
+  foStream.write(data, data.length);
+  foStream.close();
+}
+
+function readFromFile(file)
+{
+  // |file| is nsIFile
+  var data = "";
+  var fstream = Components.classes["@mozilla.org/network/file-input-stream;1"]
+                          .createInstance(Components.interfaces.nsIFileInputStream);
+  var sstream = Components.classes["@mozilla.org/scriptableinputstream;1"]
+                          .createInstance(Components.interfaces.nsIScriptableInputStream);
+  fstream.init(file, -1, 0, 0);
+  sstream.init(fstream); 
+
+  var str = sstream.read(4096);
+  while (str.length > 0) {
+    data += str;
+    str = sstream.read(4096);
+  }
+
+  sstream.close();
+  fstream.close();
+
+  return data;
+}
+
+function runProgram(commandLine)
+{
+  // create an nsILocalFile for the executable
+  var file = Components.classes["@mozilla.org/file/local;1"]
+                       .createInstance(Components.interfaces.nsILocalFile);
+  file.initWithPath("/bin/sh");
+
+  // create an nsIProcess
+  var process = Components.classes["@mozilla.org/process/util;1"]
+                          .createInstance(Components.interfaces.nsIProcess);
+  process.init(file);
+
+  // Run the process.
+  // If first param is true, calling thread will be blocked until
+  // called process terminates.
+  // Second and third params are used to pass command-line arguments
+  // to the process.
+  var args = ["-c", commandLine];
+  process.run(true, args, args.length);
+}
+
+// only for testing...
+function testIO()
+{
+  var f = makeTempFile();
+  writeToFile(f, "essai\ntest");
+  alert(readFromFile(f));
+  runProgram("zenity --info");
+}
diff --git a/gui/chrome/content/nixos-gui/main.js b/gui/chrome/content/nixos-gui/main.js
new file mode 100644
index 00000000000..baa934e43e2
--- /dev/null
+++ b/gui/chrome/content/nixos-gui/main.js
@@ -0,0 +1,171 @@
+var COPYCOL = 2;
+var gOptionListView = new treeView(["opt-success","opt-name","opt-desc"],
+                                   COPYCOL);
+
+// Run xulrunner application.ini -jsconsole -console, to see messages.
+function log(str)
+{
+  Components.classes['@mozilla.org/consoleservice;1']
+    .getService(Components.interfaces.nsIConsoleService)
+    .logStringMessage(str);
+}
+
+
+// return the DOM of the value returned by nix-instantiate
+function dumpOptions(path)
+{
+  var nixInstantiate = "nix-instantiate"; // "@nix@/bin/nix-instantiate";
+  var nixos = "/etc/nixos/nixos/default.nix"; // "@nixos@/default.nix";
+
+  var o = makeTempFile("nixos-options");
+
+  path = "eval.options" + (path? "." + path : "");
+  log("retrieve options from: " + path);
+
+  runProgram(nixInstantiate+" "+nixos+" -A "+path+" --eval-only --strict --xml 2>/dev/null | tr -d '' >" + o.path);
+
+  var xml = readFromFile(o);
+  o.remove(false);
+
+  // jQuery does a stack overflow when converting the XML to a DOM.
+  var dom = DOMParser().parseFromString(xml, "text/xml");
+  
+  log("return dom");
+  return dom;
+}
+
+
+// Pretty print Nix values.
+function nixPP(value, level)
+{
+  function indent(level) {  ret = ""; while (level--) ret+= "  "; return ret; }
+
+  if (!level) level = 0;
+  var ret = "<no match>";
+  if (value.is("attrs")) {
+    var content = "";
+    value.children().each(function (){
+      var name = $(this).attr("name");
+      var value = nixPP($(this).children(), level + 1);
+      content += indent(level + 1) + name + " = " + value + ";\n";
+    });
+    ret = "{\n" + content + indent(level) + "}";
+  }
+  else if (value.is("list")) {
+    var content = "";
+    value.children().each(function (){
+      content += indent(level + 1) + "(" + nixPP($(this), level + 1) + ")\n";
+    });
+    ret = "[\n" + content + indent(level) + "]";
+  }
+  else if (value.is("bool"))
+    ret = (value.attr("value") == "true");
+  else if (value.is("string"))
+    ret = '"' + value.attr("value") + '"';
+  else if (value.is("path"))
+    ret = value.attr("value");
+  else if (value.is("int"))
+    ret = parseInt(value.attr("value"));
+  else if (value.is("derivation"))
+    ret = value.attr("outPath");
+  else if (value.is("function"))
+    ret = "<function>";
+  else {
+    var content = "";
+    value.children().each(function (){
+      content += indent(level + 1) + "(" + nixPP($(this), level + 1) + ")\n";
+    });
+    ret = "<!--" + value.selector + "--><!--\n" + content + indent(level) + "-->";
+  }
+  return ret;
+}
+
+// Function used to reproduce the select operator on the XML DOM.
+// It return the value contained in the targeted attribute.
+function nixSelect(attrs, selector)
+{
+  var names = selector.split(".");
+  var value = $(attrs);
+  for (var i = 0; i < names.length; i++) {
+    log(nixPP(value) + "." + names[i]);
+    if (value.is("attrs"))
+      value = value.children("attr[name='" + names[i] + "']").children();
+    else {
+      log("Cannot do an attribute selection.");
+      break
+    }
+  }
+
+  log("nixSelect return: " + nixPP(value));
+
+  var ret;
+  if (value.is("attrs") || value.is("list"))
+    ret = value;
+  else if (value.is("bool"))
+    ret = value.attr("value") == "true";
+  else if (value.is("string"))
+    ret = value.attr("value");
+  else if (value.is("int"))
+    ret = parseInt(value.attr("value"));
+  else if (value.is("derivation"))
+    ret = value.attr("outPath");
+  else if (value.is("function"))
+    ret = "<function>";
+
+  return ret;
+}
+
+var gProgressBar;
+function setProgress(current, max)
+{
+  if (gProgressBar) {
+    gProgressBar.value = 100 * current / max;
+    log("progress: " + gProgressBar.value + "%");
+  }
+  else
+    log("unknow progress bar");
+}
+
+// fill the list of options
+function setOptionList(optionDOM)
+{
+  var options = $("attrs", optionDOM).filter(function () {
+    return $(this)
+      .children("attr[name='_type']")
+      .children("string[value='option']")
+      .length != 0;
+  });
+
+  var max = options.length;
+
+  log("Number of options: " + max);
+
+  setProgress(0, max);
+  gOptionListView.clear();
+  options.each(function (index){
+      var success = nixSelect(this, "config.success");
+      var name = nixSelect(this, "name");
+      var desc = nixSelect(this, "description");
+      if (success && name && desc) {
+        log("Add option '" + name + "' in the list.");
+        gOptionListView.addRow([success, name, desc]);
+      }
+      else
+        log("A problem occur while scanning an option.");
+      setProgress(index + 1, max);
+  });
+}
+
+
+function onload()
+{
+  var optionList = document.getElementById("option-list");
+  gProgressBar = document.getElementById("progress-bar");
+  setProgress(0, 1);
+  optionList.view = gOptionListView;
+
+  // try to avoid blocking the rendering, unfortunately this is not perfect.
+  setTimeout(function (){
+    setOptionList(dumpOptions("hardware"));}
+  , 100);
+}
diff --git a/gui/chrome/content/nixos-gui/myviewer.xul b/gui/chrome/content/nixos-gui/myviewer.xul
new file mode 100644
index 00000000000..c0c2bd6f822
--- /dev/null
+++ b/gui/chrome/content/nixos-gui/myviewer.xul
@@ -0,0 +1,30 @@
+<?xml version="1.0"?>
+<?xml-stylesheet href="chrome://global/skin/" type="text/css"?>
+
+<!DOCTYPE window>
+
+<!-- To edit this file I recommend you to use: 
+     http://xulfr.org/outils/xulediteur.xul
+  -->
+
+<window
+  id     = "nixos-gui"
+  title  = "NixOS gui"
+  xmlns  = "http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
+  <script src="jquery-1.3.2.js"/>
+  <script src="treeView.js"/>
+  <script src="main.js"/>
+  <script src="io.js"/>
+  <tree flex="1" id="option-list" persist="height">
+    <treecols>
+      <treecol persist="hidden width" flex="1" id="opt-success" label="Success"/>
+      <splitter class="tree-splitter"/>
+      <treecol persist="hidden width" flex="30" id="opt-name" label="Option"/>
+      <splitter class="tree-splitter"/>
+      <treecol persist="hidden width" flex="50" id="opt-desc" label="Description"
+               primary="true"/>
+    </treecols>
+    <treechildren id="first-child" flex="1"/>
+  </tree>
+  <progressmeter id="progress-bar" value="0%"/>
+</window>
diff --git a/gui/chrome/content/nixos-gui/treeView.js b/gui/chrome/content/nixos-gui/treeView.js
new file mode 100644
index 00000000000..8ab7c875e68
--- /dev/null
+++ b/gui/chrome/content/nixos-gui/treeView.js
@@ -0,0 +1,117 @@
+// Taken from pageInfo.js
+
+//******** define a js object to implement nsITreeView
+function treeView(columnids, copycol)
+{
+  // columnids is an array of strings indicating the names of the columns, in order
+  this.columnids = columnids;
+  this.colcount = columnids.length;
+
+  // copycol is the index number for the column that we want to add to
+  // the copy-n-paste buffer when the user hits accel-c
+  this.copycol = copycol;
+  this.rows = 0;
+  this.tree = null;
+  this.data = [ ];
+  this.selection = null;
+  this.sortcol = null;
+  this.sortdir = 0;
+}
+
+treeView.prototype = {
+  set rowCount(c) { throw "rowCount is a readonly property"; },
+  get rowCount() { return this.rows; },
+
+  setTree: function(tree)
+  {
+    this.tree = tree;
+  },
+
+  getCellText: function(row, column)
+  {
+    // row can be null, but js arrays are 0-indexed.
+    // colidx cannot be null, but can be larger than the number
+    // of columns in the array (when column is a string not in
+    // this.columnids.) In this case it's the fault of
+    // whoever typoed while calling this function.
+    return this.data[row][column.index] || "";
+  },
+
+  setCellValue: function(row, column, value)
+  {
+  },
+
+  setCellText: function(row, column, value)
+  {
+    this.data[row][column.index] = value;
+  },
+
+  addRow: function(row)
+  {
+    this.rows = this.data.push(row);
+    this.rowCountChanged(this.rows - 1, 1);
+  },
+
+  addRows: function(rows)
+  {
+    var length = rows.length;
+    for(var i = 0; i < length; i++)
+      this.rows = this.data.push(rows[i]);
+    this.rowCountChanged(this.rows - length, length);
+  },
+
+  rowCountChanged: function(index, count)
+  {
+    this.tree.rowCountChanged(index, count);
+  },
+
+  invalidate: function()
+  {
+    this.tree.invalidate();
+  },
+
+  clear: function()
+  {
+    if (this.tree)
+      this.tree.rowCountChanged(0, -this.rows);
+    this.rows = 0;
+    this.data = [ ];
+  },
+
+  handleCopy: function(row)
+  {
+    return (row < 0 || this.copycol < 0) ? "" : (this.data[row][this.copycol] || "");
+  },
+
+  performActionOnRow: function(action, row)
+  {
+    if (action == "copy") {
+      var data = this.handleCopy(row)
+      this.tree.treeBody.parentNode.setAttribute("copybuffer", data);
+    }
+  },
+
+  getRowProperties: function(row, prop) { },
+  getCellProperties: function(row, column, prop) { },
+  getColumnProperties: function(column, prop) { },
+  isContainer: function(index) { return false; },
+  isContainerOpen: function(index) { return false; },
+  isSeparator: function(index) { return false; },
+  isSorted: function() { },
+  canDrop: function(index, orientation) { return false; },
+  drop: function(row, orientation) { return false; },
+  getParentIndex: function(index) { return 0; },
+  hasNextSibling: function(index, after) { return false; },
+  getLevel: function(index) { return 0; },
+  getImageSrc: function(row, column) { },
+  getProgressMode: function(row, column) { },
+  getCellValue: function(row, column) { },
+  toggleOpenState: function(index) { },
+  cycleHeader: function(col) { },
+  selectionChanged: function() { },
+  cycleCell: function(row, column) { },
+  isEditable: function(row, column) { return false; },
+  isSelectable: function(row, column) { return false; },
+  performAction: function(action) { },
+  performActionOnCell: function(action, row, column) { }
+};
diff --git a/gui/components/clh.js b/gui/components/clh.js
new file mode 100644
index 00000000000..fd85422d6c8
--- /dev/null
+++ b/gui/components/clh.js
@@ -0,0 +1,154 @@
+const nsIAppShellService    = Components.interfaces.nsIAppShellService;
+const nsISupports           = Components.interfaces.nsISupports;
+const nsICategoryManager    = Components.interfaces.nsICategoryManager;
+const nsIComponentRegistrar = Components.interfaces.nsIComponentRegistrar;
+const nsICommandLine        = Components.interfaces.nsICommandLine;
+const nsICommandLineHandler = Components.interfaces.nsICommandLineHandler;
+const nsIFactory            = Components.interfaces.nsIFactory;
+const nsIModule             = Components.interfaces.nsIModule;
+const nsIWindowWatcher      = Components.interfaces.nsIWindowWatcher;
+
+// CHANGEME: to the chrome URI of your extension or application
+const CHROME_URI = "chrome://nixos-gui/content/myviewer.xul";
+
+// CHANGEME: change the contract id, CID, and category to be unique
+// to your application.
+const clh_contractID = "@mozilla.org/commandlinehandler/general-startup;1?type=myapp";
+
+// use uuidgen to generate a unique ID
+const clh_CID = Components.ID("{2991c315-b871-42cd-b33f-bfee4fcbf682}");
+
+// category names are sorted alphabetically. Typical command-line handlers use a
+// category that begins with the letter "m".
+const clh_category = "m-myapp";
+
+/**
+ * Utility functions
+ */
+
+/**
+ * Opens a chrome window.
+ * @param aChromeURISpec a string specifying the URI of the window to open.
+ * @param aArgument an argument to pass to the window (may be null)
+ */
+function openWindow(aChromeURISpec, aArgument)
+{
+  var ww = Components.classes["@mozilla.org/embedcomp/window-watcher;1"].
+    getService(Components.interfaces.nsIWindowWatcher);
+  ww.openWindow(null, aChromeURISpec, "_blank",
+                "chrome,menubar,toolbar,status,resizable,dialog=no",
+                aArgument);
+}
+ 
+/**
+ * The XPCOM component that implements nsICommandLineHandler.
+ * It also implements nsIFactory to serve as its own singleton factory.
+ */
+const myAppHandler = {
+  /* nsISupports */
+  QueryInterface : function clh_QI(iid)
+  {
+    if (iid.equals(nsICommandLineHandler) ||
+        iid.equals(nsIFactory) ||
+        iid.equals(nsISupports))
+      return this;
+
+    throw Components.results.NS_ERROR_NO_INTERFACE;
+  },
+
+  /* nsICommandLineHandler */
+
+  handle : function clh_handle(cmdLine)
+  {
+    openWindow(CHROME_URI, cmdLine);
+    cmdLine.preventDefault = true;
+  },
+
+  // CHANGEME: change the help info as appropriate, but
+  // follow the guidelines in nsICommandLineHandler.idl
+  // specifically, flag descriptions should start at
+  // character 24, and lines should be wrapped at
+  // 72 characters with embedded newlines,
+  // and finally, the string should end with a newline
+  helpInfo : "  <filename>           Open the file in the viewer\n",
+
+  /* nsIFactory */
+
+  createInstance : function clh_CI(outer, iid)
+  {
+    if (outer != null)
+      throw Components.results.NS_ERROR_NO_AGGREGATION;
+
+    return this.QueryInterface(iid);
+  },
+
+  lockFactory : function clh_lock(lock)
+  {
+    /* no-op */
+  }
+};
+
+/**
+ * The XPCOM glue that implements nsIModule
+ */
+const myAppHandlerModule = {
+  /* nsISupports */
+  QueryInterface : function mod_QI(iid)
+  {
+    if (iid.equals(nsIModule) ||
+        iid.equals(nsISupports))
+      return this;
+
+    throw Components.results.NS_ERROR_NO_INTERFACE;
+  },
+
+  /* nsIModule */
+  getClassObject : function mod_gch(compMgr, cid, iid)
+  {
+    if (cid.equals(clh_CID))
+      return myAppHandler.QueryInterface(iid);
+
+    throw Components.results.NS_ERROR_NOT_REGISTERED;
+  },
+
+  registerSelf : function mod_regself(compMgr, fileSpec, location, type)
+  {
+    compMgr.QueryInterface(nsIComponentRegistrar);
+
+    compMgr.registerFactoryLocation(clh_CID,
+                                    "myAppHandler",
+                                    clh_contractID,
+                                    fileSpec,
+                                    location,
+                                    type);
+
+    var catMan = Components.classes["@mozilla.org/categorymanager;1"].
+      getService(nsICategoryManager);
+    catMan.addCategoryEntry("command-line-handler",
+                            clh_category,
+                            clh_contractID, true, true);
+  },
+
+  unregisterSelf : function mod_unreg(compMgr, location, type)
+  {
+    compMgr.QueryInterface(nsIComponentRegistrar);
+    compMgr.unregisterFactoryLocation(clh_CID, location);
+
+    var catMan = Components.classes["@mozilla.org/categorymanager;1"].
+      getService(nsICategoryManager);
+    catMan.deleteCategoryEntry("command-line-handler", clh_category);
+  },
+
+  canUnload : function (compMgr)
+  {
+    return true;
+  }
+};
+
+/* The NSGetModule function is the magic entry point that XPCOM uses to find what XPCOM objects
+ * this component provides
+ */
+function NSGetModule(comMgr, fileSpec)
+{
+  return myAppHandlerModule;
+}
diff --git a/gui/defaults/preferences/myviewer-prefs.js b/gui/defaults/preferences/myviewer-prefs.js
new file mode 100644
index 00000000000..e10fa18c0d8
--- /dev/null
+++ b/gui/defaults/preferences/myviewer-prefs.js
@@ -0,0 +1,11 @@
+pref("toolkit.defaultChromeURI", "chrome://nixos-gui/content/myviewer.xul");
+pref("general.useragent.extra.myviewer", "NixOS gui/0.0");
+
+/* debugging prefs */
+pref("browser.dom.window.dump.enabled", true);  // enable output to stderr
+pref("javascript.options.showInConsole", true); // show javascript errors from chrome: files in the jsconsole
+pref("javascript.options.strict", true);        // show javascript strict warnings in the jsconsole
+
+/* disable xul cache so that modifications to chrome: files apply without restarting xulrunner */
+pref("nglayout.debug.disable_xul_cache", true); 
+pref("nglayout.debug.disable_xul_fastload", true);
diff --git a/gui/nixos-gui b/gui/nixos-gui
new file mode 100755
index 00000000000..f7728147ad3
--- /dev/null
+++ b/gui/nixos-gui
@@ -0,0 +1,3 @@
+#!/bin/sh
+
+exec xulrunner "./application.ini"