Understanding the "ionice" Command in Linux with Examples

What is the ionice Command in Linux?

The ionice command in Linux is used to set the scheduling class and priority of a process. It is a part of the util-linux package, which provides essential system utilities for the Linux operating system.

Using this command, you can set the I/O scheduling class and priority for a process or group of processes, allowing the user to give higher priority to chosen programs for disk I/O operations, thus achieving better performance.

Syntax of ionice Command

ionice [options] [command]

Options of ionice Command

The following are some of the most commonly used options of the ionice command:

• -c: Used to set the scheduling class. It can be either idle, best-effort or real-time.
• -n: Used to set the priority. This value should be in the range 0-7, with 0 being the highest priority.
• -p: Used to set the process ID of the process for which the I/O scheduling should be changed.

Examples of ionice Command

Here are some examples of how the ionice command can be used:

# Give a process (specified by PID) the highest I/O priority
ionice -c 3 -n 0 -p 12345 

# Change the I/O scheduling class for all processes with "myscript.sh" in their command name
ionice -c 2 -n 5 -p $(pgrep myscript.sh) 

# Make sure all processes currently running under the user "tom" have the highest I/O priority
ionice -c 3 -n 0 -p $(pgrep -u tom) 

# Make sure all processes currently running in the system have the lowest I/O priority
ionice -c 3 -n 7 -p $(pidof -x bash)

These examples show how versatile the ionice command can be when it comes to assigning different I/O priorities to processes.