renice — Alter priority of running processes.Summary: GNU/Linux is a multi-user and multi-tasking OS. So many processes will be running with some scheduling policy like Round Rabin, FIFO etc.. High priority process will get more CPU Time. renice is used to alters the scheduling priority of one or more running processes. Priority range goes from -20 (Highest priority) to 19 (Lowest priority). Examples:
$ renice +1 123 -- Increment the priority value of a process, which PID is 123. # renice -1 123 -- Decrement the priority value of a process,which PID is 123. (Root only can decrement). $ renice +1 -p 123 -p 200 -- Same as above. Here the number of process is 2. $ renice +1 -u bharathi -- Increment the priority value of all processes, which is owned by a user (bharathi). $ renice +1 -g backup -- Increment the priority value of all processes, which is owned by a group (backup).
NOTE: Incrementing the priority value will reduce the priority level and vice versa. Priority range is -20 (High) to 19 (Low). Read: man renice