diff --git a/system/options.nix b/system/options.nix
index f23adf9e7cf..6adb1ffb226 100644
--- a/system/options.nix
+++ b/system/options.nix
@@ -2246,7 +2246,7 @@ in
     (import ../upstart-jobs/hal.nix)
     (import ../upstart-jobs/gpm.nix)
     (import ../upstart-jobs/nagios/default.nix)
-    (import ../upstart-jobs/xserver.nix)
+    (import ../upstart-jobs/xserver/default.nix)
     (import ../upstart-jobs/zabbix-agent.nix)
     (import ../upstart-jobs/zabbix-server.nix)
     (import ../upstart-jobs/disnix.nix)
diff --git a/upstart-jobs/xserver.nix b/upstart-jobs/xserver/default.nix
similarity index 60%
rename from upstart-jobs/xserver.nix
rename to upstart-jobs/xserver/default.nix
index 9064ec15310..0a7a70c7175 100644
--- a/upstart-jobs/xserver.nix
+++ b/upstart-jobs/xserver/default.nix
@@ -66,6 +66,7 @@ let
           ";
         };
 
+/*
         sessionType = mkOption {
           default = "gnome";
           example = "xterm";
@@ -91,14 +92,6 @@ let
           ";
         };
 
-        renderingFlag = mkOption {
-          default = "";
-          example = "--indirect-rendering";
-          description = "
-            Possibly pass --indierct-rendering to Compiz.
-          ";
-        };
-
         sessionStarter = mkOption {
           example = "${pkgs.xterm}/bin/xterm -ls";
           description = "
@@ -107,6 +100,7 @@ let
             <option>services.xserver.sessionType</option> is empty.
           ";
         };
+*/
 
         startSSHAgent = mkOption {
           default = true;
@@ -118,41 +112,6 @@ let
           ";
         };
 
-        slim = {
-
-          theme = mkOption {
-            default = null;
-            example = pkgs.fetchurl {
-              url = http://download.berlios.de/slim/slim-wave.tar.gz;
-              sha256 = "0ndr419i5myzcylvxb89m9grl2xyq6fbnyc3lkd711mzlmnnfxdy";
-            };
-            description = "
-              The theme for the SLiM login manager.  If not specified, SLiM's
-              default theme is used.  See <link
-              xlink:href='http://slim.berlios.de/themes01.php'/> for a
-              collection of themes.
-            ";
-          };
-
-          defaultUser = mkOption {
-            default = "";
-            example = "login";
-            description = "
-              The default user to load. If you put a username here you
-              get it automatically loaded into the username field, and
-              the focus is placed on the password.
-            ";
-          };
-
-          hideCursor = mkOption {
-            default = false;
-            example = true;
-            description = "
-              Hide the mouse cursor on the login screen.
-            ";
-          };
-        };
-
         isClone = mkOption {
           default = true;
           example = false;
@@ -327,7 +286,6 @@ let
   # Abbreviations.
   cfg = config.services.xserver;
   xorg = cfg.package;
-  gnome = pkgs.gnome;
   stdenv = pkgs.stdenv;
 
   knownVideoDrivers = {
@@ -344,25 +302,9 @@ let
   # Get a bunch of user settings.
   videoDriver = cfg.videoDriver;
   resolutions = map (res: ''"${toString res.x}x${toString res.y}"'') (cfg.resolutions);
-  sessionType = cfg.sessionType;
 
   videoDriverModules = getAttr [ videoDriver ] (throw "unkown video driver : \"${videoDriver}\"") knownVideoDrivers;
 
-  sessionCmd =
-    if sessionType == "" then cfg.sessionStarter else
-    if sessionType == "xterm" then "${pkgs.xterm}/bin/xterm -ls" else
-    if sessionType == "gnome" then "${gnome.gnometerminal}/bin/gnome-terminal -ls" else
-    abort ("unknown session type ${sessionType}");
-
-
-  windowManager =
-    let wm = cfg.windowManager; in
-    if wm != "" then wm else
-    if sessionType == "gnome" then "metacity" else
-    if sessionType == "kde" then "none" /* started by startkde */ else
-    "twm";
-
-    
   modules = 
 
     getAttr ["modulesFirst"] [] videoDriverModules
@@ -518,244 +460,7 @@ let
   };
 
 
-  clientScript = pkgs.writeText "xclient" ''
-
-    source /etc/profile
-
-    exec > $HOME/.Xerrors 2>&1
-
-
-    ### Load X defaults.
-    if test -e ~/.Xdefaults; then
-      ${xorg.xrdb}/bin/xrdb -merge ~/.Xdefaults
-    fi
-
-
-    ${if cfg.startSSHAgent then ''
-      ### Start the SSH agent.
-      export SSH_ASKPASS=${pkgs.x11_ssh_askpass}/libexec/x11-ssh-askpass
-      eval $(${pkgs.openssh}/bin/ssh-agent)
-    '' else ""}
-
-    ### Allow user to override system-wide configuration
-    if test -f ~/.xsession; then
-        source ~/.xsession;
-    fi
-  
-
-    ### Start a window manager.
-  
-    ${if windowManager == "twm" then ''
-      ${xorg.twm}/bin/twm &
-    ''
-
-    else if windowManager == "metacity" then ''
-      env LD_LIBRARY_PATH=${xorg.libX11}/lib:${xorg.libXext}/lib:/usr/lib/
-      # !!! Hack: load the schemas for Metacity.
-      GCONF_CONFIG_SOURCE=xml::~/.gconf ${gnome.GConf}/bin/gconftool-2 \
-        --makefile-install-rule ${gnome.metacity}/etc/gconf/schemas/*.schemas # */
-      ${gnome.metacity}/bin/metacity &
-    ''
-
-    else if windowManager == "kwm" then ''
-      ${pkgs.kdebase}/bin/kwin &
-    ''
-
-    else if windowManager == "compiz" then ''
-      # !!! Hack: load the schemas for Compiz.
-      GCONF_CONFIG_SOURCE=xml::~/.gconf ${gnome.GConf}/bin/gconftool-2 \
-        --makefile-install-rule ${pkgs.compiz}/etc/gconf/schemas/*.schemas # */
-
-      # !!! Hack: turn on most Compiz modules.
-      ${gnome.GConf}/bin/gconftool-2 -t list --list-type=string \
-        --set /apps/compiz/general/allscreens/options/active_plugins \
-        [gconf,png,decoration,wobbly,fade,minimize,move,resize,cube,switcher,rotate,place,scale,water]
-
-      # Start Compiz and the GTK-style window decorator.
-      env LD_LIBRARY_PATH=${xorg.libX11}/lib:${xorg.libXext}/lib:/usr/lib/
-      ${pkgs.compiz}/bin/compiz gconf ${cfg.renderingFlag} &
-      ${pkgs.compiz}/bin/gtk-window-decorator --sync &
-    ''
-
-    else if windowManager == "xmonad" then ''
-      ${pkgs.xmonad}/bin/xmonad &
-    ''
-    
-    else if windowManager == "wmii" then ''
-      ${pkgs.wmiiSnap}/bin/wmii &
-    ''
-    
-    else if windowManager == "none" then ''
-      # The session starter will start the window manager.
-    ''
-
-    else abort ("unknown window manager " + windowManager)}
-    WMpid=$!
-
-    ### Show a background image.
-    # (but not if we're starting a full desktop environment that does it for us)
-    ${if sessionType != "kde" then ''
-    
-      if test -e $HOME/.background-image; then
-        ${pkgs.feh}/bin/feh --bg-scale $HOME/.background-image
-      fi
-      
-    '' else ""}
-    
-
-    ### Start the session.
-    ${if sessionType == "kde" then ''
-
-      # Start KDE.
-      export KDEDIRS=$HOME/.nix-profile:/nix/var/nix/profiles/default:${pkgs.kdebase}:${pkgs.kdelibs}
-      export XDG_CONFIG_DIRS=${pkgs.kdebase}/etc/xdg:${pkgs.kdelibs}/etc/xdg
-      export XDG_DATA_DIRS=${pkgs.kdebase}/share
-      exec ${pkgs.kdebase}/bin/startkde
-
-    '' else ''
-
-      # For all other session types, we currently just start a
-      # terminal of the kind indicated by sessionCmd.
-      # !!! yes, this means that you 'log out' by killing the X server.
-      while ${sessionCmd}; do
-        sleep 1
-      done
-
-    ''}
-    
-  '';
-
-
-  xserverArgs = [
-    "-ac"
-    "-logverbose"
-    "-verbose"
-    "-terminate"
-    "-logfile" "/var/log/X.${toString cfg.display}.log"
-    "-config ${configFile}"
-    ":${toString cfg.display}" "vt${toString cfg.tty}"
-    "-xkbdir" "${pkgs.xkeyboard_config}/etc/X11/xkb"
-  ] ++ optional (!config.services.xserver.tcpEnable) "-nolisten tcp";
-
-  
-  slimConfig = pkgs.writeText "slim.cfg" ''
-    xauth_path ${xorg.xauth}/bin/xauth
-    default_xserver ${xorg.xorgserver}/bin/X
-    xserver_arguments ${toString xserverArgs}
-    login_cmd exec ${stdenv.bash}/bin/sh ${clientScript}
-    halt_cmd ${pkgs.upstart}/sbin/shutdown -h now
-    reboot_cmd ${pkgs.upstart}/sbin/shutdown -r now
-    ${if cfg.slim.defaultUser != "" then "default_user " + cfg.slim.defaultUser else ""}
-    ${if cfg.slim.hideCursor then "hidecursor true" else ""}
-  '';
-
-
-  # Unpack the SLiM theme, or use the default.
-  slimThemesDir =
-    let
-      unpackedTheme = stdenv.mkDerivation {
-        name = "slim-theme";
-        buildCommand = ''
-          ensureDir $out
-          cd $out
-          unpackFile ${cfg.slim.theme}
-          ln -s * default
-        '';
-      };
-    in if cfg.slim.theme == null then "${pkgs.slim}/share/slim/themes" else unpackedTheme;       
-
-    nvidiaDrivers = (config.boot.kernelPackages pkgs).nvidiaDrivers;
-
-  oldJob = rec {
-  # Warning the indentation is wrong since here in order to don't produce noise in diffs.
-
-  name = "xserver";
-
-  
-  extraPath = [
-    xorg.xrandr
-    xorg.xrdb
-    xorg.setxkbmap
-    xorg.iceauth # required for KDE applications (it's called by dcopserver)
-    pkgs.feh
-  ]
-  ++ optional (windowManager == "twm") [
-    xorg.twm
-  ]
-  ++ optional (windowManager == "metacity") [
-    gnome.metacity
-  ]
-  ++ optional (windowManager == "compiz") [
-    pkgs.compiz
-  ]
-  ++ optional (sessionType == "xterm") [
-    pkgs.xterm
-  ]
-  ++ optional (sessionType == "gnome") [
-    gnome.gnometerminal
-    gnome.GConf
-    gnome.gconfeditor
-  ]
-  ++ optional (sessionType == "kde") [
-    pkgs.kdelibs
-    pkgs.kdebase
-    xorg.xset # used by startkde, non-essential
-  ]
-  ++ optional (videoDriver == "nvidia") [
-    kernelPackages.nvidiaDrivers
-  ];
-
-
-  extraEtc =
-    optional (sessionType == "kde")
-      { source = "${pkgs.xkeyboard_config}/etc/X11/xkb";
-        target = "X11/xkb";
-      }
-    ++
-    optional cfg.exportConfiguration
-      { source = "${configFile}";
-        target = "X11/xorg.conf";
-      };
-
-    
-  job = ''
-    start on ${if cfg.autorun then "network-interfaces" else "never"}
-
-    start script
-    
-      rm -f /var/run/opengl-driver
-      ${if videoDriver == "nvidia"        
-        then ''
-          ln -sf ${kernelPackages.nvidiaDrivers} /var/run/opengl-driver
-        ''
-        else if cfg.driSupport
-        then "ln -sf ${pkgs.mesa} /var/run/opengl-driver"
-        else ""
-       }
-
-      rm -f /var/log/slim.log
-       
-    end script
-
-    env SLIM_CFGFILE=${slimConfig}
-    env SLIM_THEMESDIR=${slimThemesDir}
-    env FONTCONFIG_FILE=/etc/fonts/fonts.conf # !!! cleanup
-    env XKB_BINDIR=${xorg.xkbcomp}/bin # Needed for the Xkb extension.
-
-    ${if videoDriver == "nvidia" 
-      then "env LD_LIBRARY_PATH=${xorg.libX11}/lib:${xorg.libXext}/lib:${kernelPackages.nvidiaDrivers}/lib" 
-      else ""
-    }
-
-    ${if videoDriver != "nvidia"
-      then "env XORG_DRI_DRIVER_PATH=${pkgs.mesa}/lib/modules/dri"
-      else ""
-    }
-
-    exec ${pkgs.slim}/bin/slim
-  '';
-  
-};
+  nvidiaDrivers = (config.boot.kernelPackages pkgs).nvidiaDrivers;
 
 in
 
@@ -763,14 +468,19 @@ mkIf cfg.enable {
   require = [
     options
 
+    # services.xserver.*Manager
+    (import ./displayManager/default.nix)
+    (import ./windowManager/default.nix)
+    (import ./desktopManager/default.nix)
+
     # services.extraJobs
-    (import ../upstart-jobs/default.nix)
+    (import ../../upstart-jobs/default.nix)
 
     # environment.etc
-    (import ../etc/default.nix)
+    (import ../../etc/default.nix)
 
     # fonts.fonts
-    (import ../system/fonts.nix)
+    (import ../../system/fonts.nix)
 
     # boot.extraModulePackages
     # security.extraSetuidPrograms
@@ -783,29 +493,77 @@ mkIf cfg.enable {
     ];
   };
 
-  security = {
-    extraSetuidPrograms = mkIf (cfg.sessionType == "kde") [
-      "kcheckpass"
+  environment = {
+    etc = mkIf cfg.exportConfiguration [
+      { source = "${configFile}";
+        target = "X11/xorg.conf";
+      }
+    ];
+
+    extraPackages = [
+      xorg.xrandr
+      xorg.xrdb
+      xorg.setxkbmap
+      xorg.iceauth # required for KDE applications (it's called by dcopserver)
+    ]
+    ++ optional (videoDriver == "nvidia") [
+      kernelPackages.nvidiaDrivers
     ];
   };
 
-  environment = {
-    etc = [
-      { source = ../etc/pam.d/kde;
-        target = "pam.d/kde";
-      }
-      { source = ../etc/pam.d/slim;
-        target = "pam.d/slim";
-      }
-    ] ++ oldJob.extraEtc;
-
-    extraPackages =
-      oldJob.extraPath;
-  };
-
   services = {
+    xserver = {
+      displayManager = {
+        xserverArgs = [
+          "-ac"
+          "-logverbose"
+          "-verbose"
+          "-terminate"
+          "-logfile" "/var/log/X.${toString cfg.display}.log"
+          "-config ${configFile}"
+          ":${toString cfg.display}" "vt${toString cfg.tty}"
+          "-xkbdir" "${pkgs.xkeyboard_config}/etc/X11/xkb"
+        ] ++ optional (!cfg.tcpEnable) "-nolisten tcp";
+      };
+    };
+
     extraJobs = [{
-      inherit (oldJob) name job;
+      name = "xserver";
+      job = ''
+        start on ${if cfg.autorun then "network-interfaces" else "never"}
+
+        start script
+        
+          rm -f /var/run/opengl-driver
+          ${if videoDriver == "nvidia"
+            then ''
+              ln -sf ${kernelPackages.nvidiaDrivers} /var/run/opengl-driver
+            ''
+            else if cfg.driSupport
+            then "ln -sf ${pkgs.mesa} /var/run/opengl-driver"
+            else ""
+           }
+
+          ${cfg.displayManager.job.beforeScript}
+          
+        end script
+
+        ${cfg.displayManager.job.env}
+        env FONTCONFIG_FILE=/etc/fonts/fonts.conf # !!! cleanup
+        env XKB_BINDIR=${xorg.xkbcomp}/bin # Needed for the Xkb extension.
+
+        ${if videoDriver == "nvidia" 
+          then "env LD_LIBRARY_PATH=${xorg.libX11}/lib:${xorg.libXext}/lib:${kernelPackages.nvidiaDrivers}/lib"
+          else ""
+        }
+
+        ${if videoDriver != "nvidia"
+          then "env XORG_DRI_DRIVER_PATH=${pkgs.mesa}/lib/modules/dri"
+          else ""
+        }
+
+        exec ${cfg.displayManager.job.execCmd}
+      '';
     }];
   };
 }
diff --git a/upstart-jobs/xserver/desktopManager/default.nix b/upstart-jobs/xserver/desktopManager/default.nix
new file mode 100644
index 00000000000..73b0308bea2
--- /dev/null
+++ b/upstart-jobs/xserver/desktopManager/default.nix
@@ -0,0 +1,76 @@
+{pkgs, config, ...}:
+
+let
+  inherit (builtins) head tail;
+  inherit (pkgs.lib) mkOption mkIf filter optionalString any;
+  cfg = config.services.xserver.desktopManager;
+
+  needBGCond = d: ! (d ? bgSupport && d.bgSupport);
+in
+
+{
+  require = [
+    (import ./kde.nix)
+    (import ./gnome.nix)
+    (import ./xterm.nix)
+    (import ./none.nix)
+  ];
+
+  services = {
+    xserver = {
+      displayManager = {
+        session = cfg.session.list;
+      };
+
+      desktopManager = {
+        session = mkOption {
+          default = [];
+          example = [{
+            name = "kde";
+            bgSupport = true;
+            start = "...";
+          }];
+          description = "
+            Internal option used to add some common line to desktop manager
+            scripts before forwarding the value to the
+            <varname>displayManager</varname>.
+          ";
+          apply = list: {
+            list = map (d: d // {
+              manage = "desktop";
+              start = d.start
+              + optionalString (needBGCond d) ''
+                if test -e $HOME/.background-image; then
+                  ${pkgs.feh}/bin/feh --bg-scale $HOME/.background-image
+                fi
+              '';
+            }) list;
+            needBGPackages = [] != filter needBGCond list;
+          };
+        };
+
+
+
+        default = mkOption {
+          default = "xterm";
+          example = "none";
+          description = "
+            Default desktop manager loaded if none have been chosen.
+          ";
+          merge = name: list:
+            let defaultDM = head list; in
+            if tail list != [] then
+              throw "Only one default desktop manager is allowed."
+            else if any (w: w.name == defaultDM) cfg.session.list then
+              defaultDM
+            else
+              throw "Default desktop manager not found.";
+        };
+      };
+    };
+  };
+
+  environment = mkIf cfg.session.needBGPackages {
+    extraPackages = [ pkgs.feh ];
+  };
+}
diff --git a/upstart-jobs/xserver/desktopManager/gnome.nix b/upstart-jobs/xserver/desktopManager/gnome.nix
new file mode 100644
index 00000000000..d6fa064ef11
--- /dev/null
+++ b/upstart-jobs/xserver/desktopManager/gnome.nix
@@ -0,0 +1,47 @@
+{pkgs, config, ...}:
+
+let
+  inherit (pkgs.lib) mkOption mkIf;
+  cfg = config.services.xserver.desktopManager.gnome;
+  gnome = pkgs.gnome;
+
+  options = { services = { xserver = { desktopManager = {
+
+    gnome = {
+      enable = mkOption {
+        default = false;
+        example = true;
+        description = "Enable a gnome terminal as a desktop manager.";
+      };
+    };
+
+  }; }; }; };
+in
+
+mkIf cfg.enable {
+  require = options;
+
+  services = {
+    xserver = {
+
+      desktopManager = {
+        session = [{
+          name = "gnome";
+          start = ''
+            ${gnome.gnometerminal}/bin/gnome-terminal -ls &
+            waitPID=$!
+          '';
+        }];
+      };
+
+    };
+  };
+
+  environment = {
+    extraPackages = [
+      gnome.gnometerminal
+      gnome.GConf
+      gnome.gconfeditor
+    ];
+  };
+}
diff --git a/upstart-jobs/xserver/desktopManager/kde.nix b/upstart-jobs/xserver/desktopManager/kde.nix
new file mode 100644
index 00000000000..9a241d77985
--- /dev/null
+++ b/upstart-jobs/xserver/desktopManager/kde.nix
@@ -0,0 +1,65 @@
+{pkgs, config, ...}:
+
+let
+  inherit (pkgs.lib) mkOption mkIf;
+  cfg = config.services.xserver.desktopManager.kde;
+  xorg = config.services.xserver.package;
+
+  options = { services = { xserver = { desktopManager = {
+
+    kde = {
+      enable = mkOption {
+        default = false;
+        example = true;
+        description = "Enable the kde desktop manager.";
+      };
+    };
+
+  }; }; }; };
+in
+
+mkIf cfg.enable {
+  require = options;
+
+  services = {
+    xserver = {
+
+      desktopManager = {
+        session = [{
+          name = "kde";
+          start = ''
+            # Start KDE.
+            export KDEDIRS=$HOME/.nix-profile:/nix/var/nix/profiles/default:${pkgs.kdebase}:${pkgs.kdelibs}
+            export XDG_CONFIG_DIRS=${pkgs.kdebase}/etc/xdg:${pkgs.kdelibs}/etc/xdg
+            export XDG_DATA_DIRS=${pkgs.kdebase}/share
+            exec ${pkgs.kdebase}/bin/startkde
+          '';
+        }];
+      };
+
+    };
+  };
+
+  security = {
+    extraSetuidPrograms = [
+      "kcheckpass"
+    ];
+  };
+
+  environment = {
+    extraPackages = [
+      pkgs.kdelibs
+      pkgs.kdebase
+      xorg.xset # used by startkde, non-essential
+    ];
+
+    etc = [
+      { source = ../../../etc/pam.d/kde;
+        target = "pam.d/kde";
+      }
+      { source = "${pkgs.xkeyboard_config}/etc/X11/xkb";
+        target = "X11/xkb";
+      }
+    ];
+  };
+}
diff --git a/upstart-jobs/xserver/desktopManager/none.nix b/upstart-jobs/xserver/desktopManager/none.nix
new file mode 100644
index 00000000000..a86bd5a7415
--- /dev/null
+++ b/upstart-jobs/xserver/desktopManager/none.nix
@@ -0,0 +1,14 @@
+{
+  services = {
+    xserver = {
+
+      desktopManager = {
+        session = [{
+          name = "none";
+          start = "";
+        }];
+      };
+
+    };
+  };
+}
diff --git a/upstart-jobs/xserver/desktopManager/xterm.nix b/upstart-jobs/xserver/desktopManager/xterm.nix
new file mode 100644
index 00000000000..e8aa0d289cb
--- /dev/null
+++ b/upstart-jobs/xserver/desktopManager/xterm.nix
@@ -0,0 +1,44 @@
+{pkgs, config, ...}:
+
+let
+  inherit (pkgs.lib) mkOption mkIf;
+  cfg = config.services.xserver.desktopManager.xterm;
+
+  options = { services = { xserver = { desktopManager = {
+
+    xterm = {
+      enable = mkOption {
+        default = false;
+        example = true;
+        description = "Enable a xterm terminal as a desktop manager.";
+      };
+    };
+
+  }; }; }; };
+in
+
+mkIf cfg.enable {
+  require = options;
+
+  services = {
+    xserver = {
+
+      desktopManager = {
+        session = [{
+          name = "xterm";
+          start = ''
+            ${pkgs.xterm}/bin/xterm -ls &
+            waitPID=$!
+          '';
+        }];
+      };
+
+    };
+  };
+
+  environment = {
+    extraPackages = [
+      pkgs.xterm
+    ];
+  };
+}
diff --git a/upstart-jobs/xserver/displayManager/default.nix b/upstart-jobs/xserver/displayManager/default.nix
new file mode 100644
index 00000000000..2699e34ecad
--- /dev/null
+++ b/upstart-jobs/xserver/displayManager/default.nix
@@ -0,0 +1,172 @@
+{pkgs, config, ...}:
+
+let
+  inherit (builtins) head tail;
+  inherit (pkgs.lib) mkOption optionals filter concatMap concatMapStrings;
+  cfg = config.services.xserver;
+  xorg = cfg.package;
+
+  # file provided by services.xserver.displayManager.session.script
+  xsession = wm: dm: pkgs.writeText "xsession" ''
+
+    source /etc/profile
+
+    exec > $HOME/.Xerrors 2>&1
+
+
+    ### Load X defaults.
+    if test -e ~/.Xdefaults; then
+      ${xorg.xrdb}/bin/xrdb -merge ~/.Xdefaults
+    fi
+
+    ${if cfg.startSSHAgent then ''
+      ### Start the SSH agent.
+      export SSH_ASKPASS=${pkgs.x11_ssh_askpass}/libexec/x11-ssh-askpass
+      eval $(${pkgs.openssh}/bin/ssh-agent)
+    '' else ""}
+
+    ### Allow user to override system-wide configuration
+    if test -f ~/.xsession; then
+        source ~/.xsession;
+    fi
+
+    # this script expect to have as first argument the following input
+    # "desktop-manager + window-manager".
+    arg="$1"
+
+    # extract the window manager.
+    windowManager="''${arg##* + }"
+    : ''${windowManager:=${cfg.windowManager.default}}
+    # extract the desktop manager.
+    desktopManager="''${arg% + *}"
+    : ''${desktopManager:=${cfg.desktopManager.default}}
+
+    # used to restart the xserver.
+    waitPID=0
+
+    # handle window manager starts.
+    case $windowManager in
+      ${concatMapStrings (s: "
+        (${s.name})
+          ${s.start}
+          ;;
+      ") wm}
+      (*) echo "$0: Window manager '$windowManager' not found.";;
+    esac
+
+    # handle desktop manager starts.
+    case $desktopManager in
+      ${concatMapStrings (s: "
+        (${s.name})
+          ${s.start}
+          ;;
+      ") dm}
+      (*) echo "$0: Desktop manager '$desktopManager' not found.";;
+    esac
+
+    test "$waitPID" != 0 && wait "$waitPID"
+    exit
+  '';
+
+in
+
+{
+  # list of display managers.
+  require = [
+    (import ./slim.nix)
+  ];
+
+  services = {
+    xserver = {
+      displayManager = {
+
+        xauthBin = mkOption {
+          default = "${xorg.xauth}/bin/xauth";
+          description = "
+            Path to the xauth binary used by display managers.
+          ";
+        };
+
+        xserverBin = mkOption {
+          default = "${xorg.xorgserver}/bin/X";
+          description = "
+            Path to the xserver binary used by display managers.
+          ";
+        };
+
+        xserverArgs = mkOption {
+          default = [];
+          example = [
+            "-ac"
+            "-logverbose"
+            "-nolisten tcp"
+          ];
+          description = "
+            List of arguments which have to be pass to when
+            the display manager start the xserver.
+          ";
+          apply = toString;
+        };
+
+        session = mkOption {
+          default = [];
+          example = [
+            {
+              manage = "desktop";
+              name = "xterm";
+              start = "
+                ${pkgs.xterm}/bin/xterm -ls &
+                waitPID=$!
+              ";
+            }
+          ];
+          description = ''
+            List of session supported with the command used to start each
+            session.  Each session script can set the
+            <varname>waitPID</varname> shell variable to make this script
+            waiting until the end of the user session.  Each script is used
+            to define either a windows manager or a desktop manager.  These
+            can be differentiated by setting the attribute
+            <varname>manage</varname> either to <literal>"window"</literal>
+            or <literal>"desktop"</literal>.
+
+            The list of desktop manager and window manager should appear
+            inside the display manager with the desktop manager name
+            followed by the window manager name.
+          '';
+          apply = list: rec {
+            wm = filter (s: s.manage == "window") list;
+            dm = filter (s: s.manage == "desktop") list;
+            names = concatMap (d: map (w: d.name + " + " + w.name) wm) dm;
+            script = xsession wm dm;
+          };
+        };
+
+        job = mkOption {
+          default = {};
+          example = {
+            beforeScript = ''
+              rm -f /var/log/slim.log
+            '';
+            env = ''
+              env SLIM_CFGFILE=/etc/slim.conf
+            '';
+            execCmd = "${pkgs.slim}/bin/slim";
+          };
+
+          description = "
+            List of arguments which have to be pass to when
+            the display manager start the xserver.
+          ";
+
+          merge = name: list:
+            if tail list != [] then
+              throw "only one display manager is allowed."
+            else
+              head list;
+        };
+
+      };
+    };
+  };
+}
diff --git a/upstart-jobs/xserver/displayManager/slim.nix b/upstart-jobs/xserver/displayManager/slim.nix
new file mode 100644
index 00000000000..8363a7a14ee
--- /dev/null
+++ b/upstart-jobs/xserver/displayManager/slim.nix
@@ -0,0 +1,112 @@
+{pkgs, config, ...}:
+
+###### interface
+let
+  inherit (pkgs.lib) mkOption;
+
+  options = { services = { xserver = {
+
+    slim = {
+
+      theme = mkOption {
+        default = null;
+        example = pkgs.fetchurl {
+          url = http://download.berlios.de/slim/slim-wave.tar.gz;
+          sha256 = "0ndr419i5myzcylvxb89m9grl2xyq6fbnyc3lkd711mzlmnnfxdy";
+        };
+        description = "
+          The theme for the SLiM login manager.  If not specified, SLiM's
+          default theme is used.  See <link
+          xlink:href='http://slim.berlios.de/themes01.php'/> for a
+          collection of themes.
+        ";
+      };
+
+      defaultUser = mkOption {
+        default = "";
+        example = "login";
+        description = "
+          The default user to load. If you put a username here you
+          get it automatically loaded into the username field, and
+          the focus is placed on the password.
+        ";
+      };
+
+      hideCursor = mkOption {
+        default = false;
+        example = true;
+        description = "
+          Hide the mouse cursor on the login screen.
+        ";
+      };
+    };
+
+  }; /* xserver */ }; /* services */ };
+
+in
+
+###### implementation
+let
+  xcfg = config.services.xserver;
+  dmcfg = xcfg.displayManager;
+  cfg = xcfg.slim;
+
+  slimConfig = pkgs.writeText "slim.cfg" ''
+    xauth_path ${dmcfg.xauthBin}
+    default_xserver ${dmcfg.xserverBin}
+    xserver_arguments ${dmcfg.xserverArgs}
+    sessions ${pkgs.lib.concatStringsSep "," dmcfg.session.names}
+    login_cmd exec ${pkgs.stdenv.bash}/bin/sh ${dmcfg.session.script} "%session"
+    halt_cmd ${pkgs.upstart}/sbin/shutdown -h now
+    reboot_cmd ${pkgs.upstart}/sbin/shutdown -r now
+    ${if cfg.defaultUser != "" then "default_user " + cfg.defaultUser else ""}
+    ${if cfg.hideCursor then "hidecursor true" else ""}
+  '';
+
+
+  # Unpack the SLiM theme, or use the default.
+  slimThemesDir =
+    let
+      unpackedTheme = pkgs.stdenv.mkDerivation {
+        name = "slim-theme";
+        buildCommand = ''
+          ensureDir $out
+          cd $out
+          unpackFile ${cfg.theme}
+          ln -s * default
+        '';
+      };
+    in if cfg.theme == null then "${pkgs.slim}/share/slim/themes" else unpackedTheme;
+
+in
+
+{
+  require = [
+    options
+  ];
+
+  services = {
+    xserver = {
+      displayManager = {
+        job = {
+          beforeScript = ''
+            rm -f /var/log/slim.log
+          '';
+          env = ''
+            env SLIM_CFGFILE=${slimConfig}
+            env SLIM_THEMESDIR=${slimThemesDir}
+          '';
+          execCmd = "${pkgs.slim}/bin/slim";
+        };
+      };
+    };
+  };
+
+  environment = {
+    etc = [
+      { source = ../../../etc/pam.d/slim;
+        target = "pam.d/slim";
+      }
+    ];
+  };
+}
diff --git a/upstart-jobs/xserver/windowManager/compiz.nix b/upstart-jobs/xserver/windowManager/compiz.nix
new file mode 100644
index 00000000000..e99c3adb5b4
--- /dev/null
+++ b/upstart-jobs/xserver/windowManager/compiz.nix
@@ -0,0 +1,64 @@
+{pkgs, config, ...}:
+
+let
+  inherit (pkgs.lib) mkOption mkIf;
+  cfg = config.services.xserver.windowManager.compiz;
+  xorg = config.services.xserver.package;
+  gnome = pkgs.gnome;
+
+  options = { services = { xserver = { windowManager = {
+
+    compiz = {
+      enable = mkOption {
+        default = false;
+        example = true;
+        description = "Enable the compiz window manager.";
+      };
+
+
+      renderingFlag = mkOption {
+        default = "";
+        example = "--indirect-rendering";
+        description = "
+          Possibly pass --indierct-rendering to Compiz.
+        ";
+      };
+    };
+
+  }; }; }; };
+in
+
+mkIf cfg.enable {
+  require = options;
+
+  services = {
+    xserver = {
+
+      windowManager = {
+        session = [{
+          name = "compiz";
+          start = ''
+            # !!! Hack: load the schemas for Compiz.
+            GCONF_CONFIG_SOURCE=xml::~/.gconf ${gnome.GConf}/bin/gconftool-2 \
+              --makefile-install-rule ${pkgs.compiz}/etc/gconf/schemas/*.schemas # */
+
+            # !!! Hack: turn on most Compiz modules.
+            ${gnome.GConf}/bin/gconftool-2 -t list --list-type=string \
+              --set /apps/compiz/general/allscreens/options/active_plugins \
+              [gconf,png,decoration,wobbly,fade,minimize,move,resize,cube,switcher,rotate,place,scale,water]
+
+            # Start Compiz and the GTK-style window decorator.
+            env LD_LIBRARY_PATH=${xorg.libX11}/lib:${xorg.libXext}/lib:/usr/lib/
+            ${pkgs.compiz}/bin/compiz gconf ${cfg.renderingFlag} &
+            ${pkgs.compiz}/bin/gtk-window-decorator --sync &
+          '';
+        }];
+      };
+
+    };
+  };
+
+  environment = {
+    extraPackages = [ pkgs.compiz ];
+  };
+}
diff --git a/upstart-jobs/xserver/windowManager/default.nix b/upstart-jobs/xserver/windowManager/default.nix
new file mode 100644
index 00000000000..41c3ad15983
--- /dev/null
+++ b/upstart-jobs/xserver/windowManager/default.nix
@@ -0,0 +1,61 @@
+{pkgs, config, ...}:
+
+let
+  inherit (builtins) head tail;
+  inherit (pkgs.lib) mkOption any;
+  cfg = config.services.xserver.windowManager;
+in
+
+{
+  require = [
+    (import ./compiz.nix)
+    (import ./kwm.nix)
+    (import ./metacity.nix)
+    (import ./none.nix)
+    (import ./twm.nix)
+    (import ./wmii.nix)
+    (import ./xmonad.nix)
+  ];
+
+  services = {
+    xserver = {
+      displayManager = {
+        session = cfg.session;
+      };
+
+      windowManager = {
+        session = mkOption {
+          default = [];
+          example = [{
+            name = "wmii";
+            start = "...";
+          }];
+          description = "
+            Internal option used to add some common line to window manager
+            scripts before forwarding the value to the
+            <varname>displayManager</varname>.
+          ";
+          apply = map (d: d // {
+            manage = "window";
+          });
+        };
+
+        default = mkOption {
+          default = "none";
+          example = "wmii";
+          description = "
+            Default window manager loaded if none have been chosen.
+          ";
+          merge = name: list:
+            let defaultWM = head list; in
+            if tail list != [] then
+              throw "Only one default window manager is allowed."
+            else if any (w: w.name == defaultWM) cfg.session then
+              defaultWM
+            else
+              throw "Default window manager not found.";
+        };
+      };
+    };
+  };
+}
diff --git a/upstart-jobs/xserver/windowManager/kwm.nix b/upstart-jobs/xserver/windowManager/kwm.nix
new file mode 100644
index 00000000000..db8696c510d
--- /dev/null
+++ b/upstart-jobs/xserver/windowManager/kwm.nix
@@ -0,0 +1,46 @@
+{pkgs, config, ...}:
+
+let
+  inherit (pkgs.lib) mkOption mkIf;
+  cfg = config.services.xserver.windowManager.kwm;
+
+  option = { services = { xserver = { windowManager = {
+
+    kwm = {
+      enable = mkOption {
+        default = false;
+        example = true;
+        description = "Enable the kwm window manager.";
+      };
+
+    };
+
+  }; }; }; };
+in
+
+mkIf cfg.enable {
+  require = option;
+
+  services = {
+    xserver = {
+
+      windowManager = {
+        session = [{
+          name = "kwm";
+          start = "
+            ${pkgs.kdebase}/bin/kwin &
+            waitPID=$!
+          ";
+        }];
+      };
+
+    };
+  };
+
+  environment = {
+    extraPackages = [
+      pkgs.kdelibs
+      pkgs.kdebase
+    ];
+  };
+}
diff --git a/upstart-jobs/xserver/windowManager/metacity.nix b/upstart-jobs/xserver/windowManager/metacity.nix
new file mode 100644
index 00000000000..dc1ff911d65
--- /dev/null
+++ b/upstart-jobs/xserver/windowManager/metacity.nix
@@ -0,0 +1,49 @@
+{pkgs, config, ...}:
+
+let
+  inherit (pkgs.lib) mkOption mkIf;
+  cfg = config.services.xserver.windowManager.metacity;
+  xorg = config.services.xserver.package;
+  gnome = pkgs.gnome;
+
+  option = { services = { xserver = { windowManager = {
+
+    metacity = {
+      enable = mkOption {
+        default = false;
+        example = true;
+        description = "Enable the metacity window manager.";
+      };
+
+    };
+
+  }; }; }; };
+in
+
+mkIf cfg.enable {
+  require = option;
+
+  services = {
+    xserver = {
+
+      windowManager = {
+        session = [{
+          name = "metacity";
+          start = ''
+            env LD_LIBRARY_PATH=${xorg.libX11}/lib:${xorg.libXext}/lib:/usr/lib/
+            # !!! Hack: load the schemas for Metacity.
+            GCONF_CONFIG_SOURCE=xml::~/.gconf ${gnome.GConf}/bin/gconftool-2 \
+              --makefile-install-rule ${gnome.metacity}/etc/gconf/schemas/*.schemas # */
+            ${gnome.metacity}/bin/metacity &
+            waitPID=$!
+          '';
+        }];
+      };
+
+    };
+  };
+
+  environment = {
+    extraPackages = [ gnome.metacity ];
+  };
+}
diff --git a/upstart-jobs/xserver/windowManager/none.nix b/upstart-jobs/xserver/windowManager/none.nix
new file mode 100644
index 00000000000..84cf1d77077
--- /dev/null
+++ b/upstart-jobs/xserver/windowManager/none.nix
@@ -0,0 +1,12 @@
+{
+  services = {
+    xserver = {
+      windowManager = {
+        session = [{
+          name = "none";
+          start = "";
+        }];
+      };
+    };
+  };
+}
diff --git a/upstart-jobs/xserver/windowManager/twm.nix b/upstart-jobs/xserver/windowManager/twm.nix
new file mode 100644
index 00000000000..f26be48776c
--- /dev/null
+++ b/upstart-jobs/xserver/windowManager/twm.nix
@@ -0,0 +1,44 @@
+{pkgs, config, ...}:
+
+let
+  inherit (pkgs.lib) mkOption mkIf;
+  cfg = config.services.xserver.windowManager.twm;
+  xorg = config.services.xserver.package;
+
+  option = { services = { xserver = { windowManager = {
+
+    twm = {
+      enable = mkOption {
+        default = false;
+        example = true;
+        description = "Enable the twm window manager.";
+      };
+
+    };
+
+  }; }; }; };
+in
+
+mkIf cfg.enable {
+  require = option;
+
+  services = {
+    xserver = {
+
+      windowManager = {
+        session = [{
+          name = "twm";
+          start = "
+            ${xorg.twm}/bin/twm &
+            waitPID=$!
+          ";
+        }];
+      };
+
+    };
+  };
+
+  environment = {
+    extraPackages = [ xorg.twm ];
+  };
+}
diff --git a/upstart-jobs/xserver/windowManager/wmii.nix b/upstart-jobs/xserver/windowManager/wmii.nix
new file mode 100644
index 00000000000..59a88f9352f
--- /dev/null
+++ b/upstart-jobs/xserver/windowManager/wmii.nix
@@ -0,0 +1,32 @@
+{pkgs, config, ...}:
+
+let
+  inherit (pkgs.lib) mkOption mkIf;
+  cfg = config.services.xserver.windowManager.wmii;
+in
+
+{
+  services = {
+    xserver = {
+
+      windowManager = {
+        wmii = {
+          enable = mkOption {
+            default = false;
+            example = true;
+            description = "Enable the wmii window manager.";
+          };
+        };
+
+        session = mkIf cfg.enable [{
+          name = "wmii";
+          start = "
+            ${pkgs.wmiiSnap}/bin/wmii &
+            waitPID=$!
+          ";
+        }];
+      };
+
+    };
+  };
+}
diff --git a/upstart-jobs/xserver/windowManager/xmonad.nix b/upstart-jobs/xserver/windowManager/xmonad.nix
new file mode 100644
index 00000000000..6f73ad9edc3
--- /dev/null
+++ b/upstart-jobs/xserver/windowManager/xmonad.nix
@@ -0,0 +1,32 @@
+{pkgs, config, ...}:
+
+let
+  inherit (pkgs.lib) mkOption mkIf;
+  cfg = config.services.xserver.windowManager.xmonad;
+in
+
+{
+  services = {
+    xserver = {
+
+      windowManager = {
+        xmonad = {
+          enable = mkOption {
+            default = false;
+            example = true;
+            description = "Enable the xmonad window manager.";
+          };
+        };
+
+        session = mkIf cfg.enable [{
+          name = "xmonad";
+          start = "
+            ${pkgs.xmonad}/bin/xmonad &
+            waitPID=$!
+          ";
+        }];
+      };
+
+    };
+  };
+}
diff --git a/upstart-jobs/xserver.conf b/upstart-jobs/xserver/xserver.conf
similarity index 100%
rename from upstart-jobs/xserver.conf
rename to upstart-jobs/xserver/xserver.conf