Change niceness (priority) of a running process

Question

Is it possible to set a new nice level of a running process with a known id?

Does this operation require root access, or just being the owner of the process?

Answer 1

Terminal

If you're at a terminal you can use renice

renice [-n] priority [[-p] pid ...] [[-g] pgrp ...] [[-u] user ...]

A simple example would be

renice 8 31043
31043: old priority 5, new priority 8

You can also pass it hard flags, but it follows that order

renice -p 31043 -n 5
31043: old priority 8, new priority 5

Priorities work on a scale of -20 tp 20 - The lower the number, the higher it's priority on the system.

If you own the process then you won't need root - however, if the process is owned by another user or if you plan on changing the group/user of the process root (via sudo) will be required.

Answer 2

GUI

• Alt+F2 and type sudo gnome-system-monitor

Prior to 11.04: System > Administration > System Monitor. Choose Processes.
In 11.04: Alt+A and search for system monitor.

The id's are shown in the image here:

And nice does not require sudo for increasing niceness if you own the task. It does if you need to decrease niceness.

Answer 3

Usage of "renice" in terminal is as follows:

Usage:
 renice [-n] <priority> [-p] <pid> [<pid>  ...]
 renice [-n] <priority> [-g] <pgrp> [<pgrp> ...]
 renice [-n] <priority> [-u] <user> [<user> ...]

Options:
 -g, --pgrp <id>        interpret as process group ID
 -h, --help             print help
 -n, --priority <num>   set the nice increment value
 -p, --pid <id>         force to be interpreted as process ID
 -u, --user <name|id>   interpret as username or user ID
 -v, --version          print version

Using "sudo" before command "renice" elevates user to root level and an admin/root password will be required.

So e.g. if you want to elevate process with PID (process ID) 2606 from Normal priority to High priority, you would type in terminal as follows:

sudo renice -n -5 -p 2606