iotop

Start iotop (shows all processes)

$ sudo iotop

$ sudo iotop -o

$ sudo iotop -a

$ sudo iotop -P

$ sudo iotop -b -n [10]

$ sudo iotop -p [PID]

$ sudo iotop -u [username]

$ sudo iotop -d [2]

iotop [-oaPbkqtd] [-n iterations] [-p pid] [-u user]

iotop is a top-like utility for monitoring disk I/O usage by processes in real-time. It displays a live view of read/write operations per process, helping identify which applications are causing disk activity.
The display shows columns for thread/process ID, priority, user, disk read rate, disk write rate, swap-in percentage, I/O percentage, and command. The I/O percentage indicates time spent waiting for I/O operations.
Accumulated mode (-a) is useful for finding processes that perform sporadic but significant I/O. Instead of showing instantaneous bandwidth, it shows total bytes read/written since iotop started, revealing processes that did heavy I/O even briefly.
The tool requires root privileges to access I/O accounting data from the kernel's taskstats interface. The kernel must have CONFIGTASKIO_ACCOUNTING enabled (most distributions include this).
Batch mode enables logging I/O activity over time. Combined with -t for timestamps, it can diagnose intermittent I/O issues by capturing activity during problem periods.

-o, --only

Show only processes actually doing I/O.

Show accumulated I/O instead of bandwidth.

Show processes only, not threads.

Non-interactive batch mode (for logging).

Number of iterations before exiting.

Delay between updates in seconds.

Monitor specific process(es).

Monitor processes for specific user(s).

Use kilobytes instead of human-readable.

Add timestamp to each line (batch mode).

Suppress header lines (batch mode).

Left/Right arrows

Change sort column.

Reverse sort order.

Toggle showing only active processes.

Toggle showing processes/threads.

Toggle accumulated/bandwidth mode.

Quit.

Change ionice priority of selected process.

Requires root privileges. Kernel must have IO accounting enabled (CONFIGTASKIO_ACCOUNTING). Shows disk I/O, not network or other I/O. May add slight overhead. Some I/O may be attributed to kernel threads rather than user processes.

iotop was written by Guillaume Chazarain and released around 2007. It was created to fill the gap in Linux monitoring tools - while CPU and memory monitoring had top, disk I/O monitoring lacked an equivalent. The tool relies on kernel features added in Linux 2.6.20.

htop(1), top(1), iostat(1), vmstat(8), dstat(1)