Frequently Asked Question

How do I change a process's priority with nice and renice?

Every Linux process carries a "nice value" between −20 and +19. The higher (nicer) the value, the less CPU the scheduler gives the process when something else wants to run. The default is 0. nice -n 10 ./my-job starts a job at nice 10, a polite "yield to anything interactive" setting; nice -n 19 ./my-job is the lowest priority you can pick. To change a process that is already running, use renice 5 -p 12345, or interactively press F7/F8 in htop.

Only root can decrease a nice value (i.e., raise priority), so ordinary users can only make their own processes less greedy, never more. Below the nice scale lives a separate world of real-time scheduling classes (SCHED_FIFO, SCHED_RR) set with chrt, which run ahead of every normal process and need root by default. For everyday batch work, a backup, a video transcode, a long compile, nice 10 is the right reflex.