Users can only run at a priority of 0.-default priority is 0 and root only can set priority from -20 (highest) to 19 (lowest) priority. whatever process user runs, process starts on default priority value 0. if you are root and want to set priority use: nice -n priority_value command. example: nice -n -20 find /etc -name passwd. but users cant set the priority to process. if you tried from no-root user you will get message: nice: cannot set priority: premission denied.