Failed to parse arguments: Cannot open display:

Usage: xfdesktop [OPTION?] Help Options: -h, --help Show help options --help-all Show all help options --help-gtk Show GTK+ Options --help-sm-client Show session management options Application Options: -V, --version Display version information -R, --reload Reload all settings -N, --next Advance to the next wallpaper on the current workspace -M, --menu Pop up the menu (at the current mouse position) -W, --windowlist Pop up the window list (at the current mouse position) -A, --arrange Automatically arrange all the icons on the desktop -e, --enable-debug Enable debug messages -d, --disable-debug Disable debug messages -D, --disable-wm-check Do not wait for a window manager on startup -Q, --quit Cause xfdesktop to quit --display=DISPLAY X display to use