renice

If the job is already running use:

renice 19 -p 2478

This gives the job 2478 (as identified with ps -aux) the lowest possible priority. renice -20 would give it highest priority. If the job is not yet running you can execute it with nice command:

nice +19 amule<(code>

to execute amule with lowest possible priority) and

nice -20 amule

to execute it with highest priority.