renice Command Cheat Sheet

renice alters the scheduling priority of one or more running processes.

Priority Range: -20 (Highest) to +19 (Lowest).

Synopsis

renice [-n] PRIORITY [-g|-p|-u] IDENTIFIER...

Basic Usage

Renice by PID (-p)

Change priority of process 1234 to 5 (Lower priority).

renice -n 5 -p 1234

(Standard users can only increase niceness, i.e., lower priority).

Increase Priority (Root Only)

Change priority to -10 (High priority).

sudo renice -n -10 -p 1234

Bulk Renice

Renice by User (-u)

Change priority of ALL processes owned by user alice.

sudo renice -n 10 -u alice

Renice by Process Group (-g)

Change priority of a process group.

renice -n 5 -g 500

Real World Usage

Scenario: A backup script is successfully running but slowing down the server. 1. Find PID: pgrep backup.sh -> 999 2. Make it nice: renice -n 19 -p 999 3. Now it runs only on idle CPU time.

Notes

Absolute Values: Unlike nice (which might add to current value), renice sets the absolute priority.
- renice -n 5 -p 1234 sets the value to 5, regardless of what it was before.
Permissions: You can modify your own processes (make them nicer). You need root to modify other users' processes or to make any process "less nice" (negative value).