# ionice > Get or set program I/O scheduling class and priority. > Scheduling classes: 1 (realtime), 2 (best-effort), 3 (idle). > Priority levels: 0 (the highest) - 7 (the lowest). > More information: . - Run a command with the given scheduling class and priority: `ionice -c {{scheduling_class}} -n {{priority}} {{command}}` - Set I/O scheduling [c]lass of a running process with a specific [p]id, [P]gid or [u]id: `ionice -c {{scheduling_class}} -{{p|P|u}} {{id}}` - Run a command with custom I/O scheduling [c]lass and priority: `ionice -c {{scheduling_class}} -n {{priority}} {{command}}` - Ignore failure to set the requested priority: `ionice -t -n {{priority}} -p {{pid}}` - Run the command even in case it was not possible to set the desired priority (this can happen due to insufficient privileges or an old kernel version): `ionice -t -n {{priority}} -p {{pid}}` - Print the I/O scheduling class and priority of a running process: `ionice -p {{pid}}`