Remove Restart and Shutdown events from GDM
Keep your administrators from accidentally rebooting your ltsp server:
$ gdmsetup
Local tab > unselect “Show Actions menu” (which remove shutdown, restart, etc from shutdown menu)

source
Keep your administrators from accidentally rebooting your ltsp server:
$ gdmsetup
Local tab > unselect “Show Actions menu” (which remove shutdown, restart, etc from shutdown menu)

source