Hack 101. Renice Command Examples

by Ramesh

Renice alters the scheduling priority of a running process.

How to decrease the priority of a running process? (Increase nice)

In the example below, an existing shell-script is running at nice value of 10. (6th column in the ps output)

$ ps axl | grep nice-test
0   509 13245 13216  30  10  5244  968 wait   SN   pts/1      0:00 /bin/bash ./nice-test.sh

To increase the nice value (thus reducing the priority), execute the renice command as shown below.

$ renice 16 -p 13245
13245: old priority 10, new priority 16

$ ps axl | grep nice-test
0   509 13245 13216  36  16  5244  968 wait   SN   pts/1      0:00 /bin/bash ./nice-test.sh

[Note: Now, the 6th column of the nice-test.sh (PID 13245) shows the new nice value of 16.]

How to increase the priority of a running process? (Decrease nice)

In the example below, an existing shell-script is running at a nice value of 10. (6th column in the ps output)

$ ps axl | grep nice-test
0   509 13254 13216  30  10  4412  968 wait   SN   pts/1      0:00 /bin/bash ./nice-test.sh

In increase the priority, give a lower nice value as shown below. However, only root can increase the priority of a running process, else you’ll get the following error message.

$ renice 5 -p 13254
renice: 13254: setpriority: Permission denied
Login as root to increase the priority of a running process

$ su -

# renice 5 -p 13254
13254: old priority 10, new priority 5

# ps axl | grep nice-test
0   509 13254 13216  25   5  4412  968 wait   SN   pts/1      0:00 /bin/bash ./nice-test.sh

[Note: The 6th column now shows a lower nice value of 5 (increased priority)]

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