Как в .desktop указать $USER ?

[Desktop Entry]
Name=Desktop
Comment=Desktop
Encoding=UTF-8
Exec=ltsp-localapps /opt/2X/Client/bin/appserverclient -s192.168.0.1 -u$USER -mMS -D"Home=/home/$USER"
Icon=gksu-root-terminal
StartupNotify=true
Terminal=false
X-MultipleArgs=false
Type=Application
Categories=GTK;Utility;TerminalEmulator;