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Nice and Renice Command in Linux with Examples

In Linux, managing process priority is crucial for optimizing system performance, especially in environments where multiple processes compete for CPU resources. The nice and renice commands allow users to adjust the scheduling priority of processes, influencing how the Linux kernel allocates CPU time among them.

• ‘nice’ Command: This command is used to start a new process with a specific priority, known as the “nice value.” A higher nice value lowers the process’s priority, while a lower (negative) nice value increases it. Processes with higher priority receive more CPU time.
• ‘renice’ Command: Unlike nice, which sets the priority when starting a process, renice modifies the priority of an already running process. This flexibility allows system administrators to manage process priorities based on the current system load dynamically. 

Working with ‘nice’ and ‘renice’ Command

Here are some practical ways to use ‘nice’ and ‘renice’ commands to manage process priorities effectively:

1. To check the nice value of a process. 

To check the current nice value of a specific process, you can use the ‘ps’ command combined with ‘grep’:

ps -el | grep terminal

The eight highlighted value is the nice value of the process. 

2. To set the priority of a process 

To start a new process with a specific nice value, use the nice command:

nice -10 gnome-terminal

This sets the nice value of the gnome-terminal process to ’10’, lowering its priority compared to processes with a nice value closer to ‘0’ or negative values.

3. To set the negative priority for a process 

To give a process higher priority by assigning a negative nice value, use:

nice --10 gnome-terminal

Negative nice values increase the process’s priority, allowing it to receive more CPU time. This is especially useful for critical tasks that need to run faster.

4. Changing priority of the running process. 

To modify the priority of an already running process, use the ‘renice’ command with the process ID (PID):

sudo renice -n 15 -p 77982

This will change the priority of the process with pid 77982. 

5. To change the priority of all programs of a specific group. 

You can also adjust the priority of all processes within a specific group by specifying the group ID (GID):

renice -n 10 -g 4

This command will set all the processes of gid 4 priority to 10, reducing their CPU time allocation.

6. To change the priority of all programs of a specific user. 

To change the priority of all processes belonging to a specific user, use the renice command with the user ID (UID):

sudo renice -n 10 -u 2

This will set all the processes of user 2 to 10, making them lower priority.

Conclusion

The ‘nice’ and ‘renice’ commands in Linux provide powerful tools for managing process scheduling priorities, allowing system administrators and users to control how CPU resources are allocated among running processes. By understanding and using these commands effectively, you can optimize system performance, ensure critical applications receive the necessary resources, and maintain a balanced workload on your Linux system.