iotop

Additional Notes

iotop is a top-like, real-time view of disk I/O grouped by process or thread. It shows how much each process is reading and writing, which makes it the fastest way to find what is hammering a disk.

It relies on kernel I/O accounting, so it usually needs root privileges. If a process shows no I/O, the kernel may not be accounting it.

Syntax

iotop [options]

Parameters

• options: Flags that filter or change the display.

Common Options

• -o, --only: Show only processes doing I/O (hides idle ones).
• -b, --batch: Batch mode for scripts; does not redraw the screen.
• -n N, --iter=NUM: Number of iterations in batch mode, then exit.
• -d SEC, --delay=SEC: Delay between updates (default 1s).
• -p PID, --pid=PID: Monitor only a specific PID.
• -u USER: Show only a given user's processes.
• -P, --processes: Show processes instead of threads.
• -a, --accumulated: Show accumulated I/O since start, not per-second rates.
• -k: Use kilobytes per second.
• -q, --quiet: Less verbose display.

Examples

sudo iotop

Show the live, full-screen I/O view (needs root).

sudo iotop -o

Show only processes that are actively doing I/O.

sudo iotop -oPa

Accumulated per-process I/O, skipping idle processes.

sudo iotop -b -n 5 -d 2

Batch mode: print five reports, two seconds apart.

sudo iotop -p 1234

Watch only PID 1234.

Practical Notes

• Run with sudo; without privileges most I/O is hidden.
• Use -o to cut through noise and find the busy writer quickly.
• -a is great for "what used the most disk since I started watching?".
• Pair with iostat -x for a device-vs-process view of the same load.
• If a process shows nothing, its I/O may not be kernel-accounted.