ionice

Updated

July 31, 2026

Overview

ionice sets or shows I/O scheduling class and priority for a process (CFQ/BFQ era semantics; effect varies by scheduler and kernel).

Syntax

ionice [options] command
ionice [options] -p PID

Classes

Class -c Meaning
None 0 Default
Realtime 1 Highest (careful; root)
Best-effort 2 Normal (priority 0–7)
Idle 3 Only when disk idle

Examples with Explanations

ionice -c3 ./heavy-backup.sh          # idle class
ionice -c2 -n7 tar -czf out.tgz big/  # best-effort low prio
ionice -p 1234                        # show
sudo ionice -c2 -n0 -p 1234           # raise I/O prio

Combined with nice

nice -n 19 ionice -c3 rsync -a /data/ /mnt/backup/