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renice

While nice is used to set the priority of a process when it starts, renice is used to alter the scheduling priority (niceness) of one or more already running processes.

  • Niceness Range: -20 (highest priority) to 19 (lowest priority).
  • As with nice, normal users can only increase the niceness (lower the priority) of their own processes. Only root can decrease the niceness (raise the priority) or change the niceness of other users' processes.

Basic Syntax​

renice [-n] PRIORITY [OPTIONS] TARGET...

(Unlike nice where you provide an adjustment, renice takes the absolute priority value you want to set).

Common Flags/Options​

OptionDescription
-p, --pidInterpret targets as Process IDs (PIDs). This is the default.
-u, --userInterpret targets as usernames. Changes priority for all processes owned by the user.
-g, --pgrpInterpret targets as process group IDs.

Real-world Examples​

1. Lower the priority of a running process​

Suppose you started a rendering job (PID 3405) normally, but now realize it's making your system sluggish. You can lower its priority by setting its nice value to 10.

renice 10 -p 3405

2. Raise the priority of a critical process (Root only)​

If a database process (PID 892) is struggling to keep up with queries, an admin can give it higher priority (a negative nice value).

sudo renice -5 -p 892

3. Change priority for all processes of a specific user​

If a specific user (e.g., a data analyst) is running multiple heavy jobs, you can lower the priority of all their processes at once.

sudo renice 15 -u alice

4. Using renice interactively in top or htop​

While renice is a command-line tool, it's often easier to change priorities interactively.

  • In top, press r, enter the PID, then enter the nice value.
  • In htop, select the process and press F7 (decrease priority/increase nice) or F8 (increase priority/decrease nice).