Here some handy notes!
-n –20 => HIGHEST
-n 19 => LOWEST
$ ps axl
nice -10 <command name> and nice -n 10 <command name> will do the same thing (both the above commands will make the process priority to the value 10).
A major misconception about nice command is that nice -10 <command name> will run that process with -10 (a higher priority).
In order to assign -10 priority to a command then you should run it as shown below.
nice –10 <command name>
Renice (change priority of a running process).
Example – put a PID to LOWER priority
$ renice 19 PID