The renice command is used to change the priority of a running process in Linux. The priority of a process determines how much CPU time it receives relative to other processes. Higher priority processes receive more CPU time, while lower priority processes receive less.
Here's an example of how to use the renice command to change the priority of a running process:
renice +5 pid
This will increase the priority of the process with the process ID (PID) pid by 5.
You can also specify a negative value to decrease the priority of the process. For example:
renice -5 pid
This will decrease the priority of the process with PID pid by 5.
Note that you will need to have the appropriate permissions to change the priority of a process. In most cases, only the root user or the owner of the process can change the priority of a process.