diff -up ./utils/gdmflexiserver.lock ./utils/gdmflexiserver
--- ./utils/gdmflexiserver.lock	2013-10-09 06:16:00.000000000 +0300
+++ ./utils/gdmflexiserver	2013-10-31 20:25:19.510330296 +0200
@@ -9,9 +9,47 @@
 #
 # See http://www.gnu.org/copyleft/gpl.html for the full text of the license.
 
+PATH=/usr/local/bin:/bin:/usr/bin
+export PATH
+
 if [ -z "$XDG_SEAT_PATH" ]; then
   # something went wrong
   exit 1
 fi
 
+find_command () {
+    cmd="$1"
+    oIFS="${IFS}"; IFS=:
+    set -- ${PATH}
+    IFS="${oIFS}"
+
+    for part; do
+        [ -x "${part}/${cmd}" ] && return 0
+    done
+    return 1
+}
+
+lock_screen () {
+    for lock_cmd in \
+        "xscreensaver-command -lock" \
+        "gnome-screensaver-command --lock" \
+        "dbus-send --session --dest=org.freedesktop.ScreenSaver --type=method_call /ScreenSaver org.freedesktop.ScreenSaver.Lock"
+    do
+        ${lock_cmd} >/dev/null 2>&1 && return
+    done
+
+    for lock_cmd in \
+        "slock" \
+        "xlock -mode blank"
+    do
+        set -- ${lock_cmd}
+        if find_command "$1"; then
+            ${lock_cmd} >/dev/null 2>&1 &
+            return
+        fi
+    done
+}
+
+lock_screen
+
 dbus-send --system --type=method_call --print-reply --dest=org.freedesktop.DisplayManager $XDG_SEAT_PATH org.freedesktop.DisplayManager.Seat.SwitchToGreeter