renice

Overview

The renice command alters the scheduling priority of running processes. It allows you to change the nice value of processes that are already running.

Syntax

renice [-n] priority [-g|-p|-u] identifier...

Common Options

Option	Description
`-n`	Specify nice increment
`-g`	Interpret as process groups
`-p`	Interpret as process IDs
`-u`	Interpret as usernames
`--help`	Display help
`--version`	Show version

Nice Values

Range: -20 to 19
Lower values = higher priority
Higher values = lower priority
Only root can set negative values
Default: current nice value

Key Use Cases

Adjust process priority
Resource management
Performance tuning
System optimization
Process control

Examples with Explanations

Example 1: Basic Usage

renice +5 -p 1234

Change priority of PID 1234

Example 2: User Processes

renice 10 -u username

Change priority of user’s processes

Example 3: Process Group

renice -5 -g 100

Change priority of process group

Understanding Output

Format:

1234: old priority 0, new priority 5

Error messages for: - Permission denied - Invalid priority - Process not found - User not found

Common Usage Patterns

Lower process priority:
```
renice +10 -p $(pgrep firefox)
```
Increase user priority:
```
sudo renice -5 -u apache
```
Multiple processes:
```
renice 5 -p 1234 5678
```

Performance Analysis

Priority impact
System load effect
Resource allocation
Process behavior
Scheduling changes

Additional Resources

Best Practices

Monitor system impact
Document changes
Consider dependencies
Regular review
Use appropriate values

Use Cases

Performance tuning
Resource allocation
System maintenance
Service optimization
Troubleshooting