iotop

iotop is a Linux command-line utility that monitors I/O usage by processes and threads in real time. It provides a top-like view of disk read and write rates, I/O wait time, and per-process statistics, enabling administrators to identify processes that drive disk I/O.

The program gathers data by reading per-process I/O counters from /proc/[pid]/io and combining them with the kernel's current I/O activity. It can show the amount of data read and written per second, the cumulative I/O, and the percentage of time a process spends waiting for I/O. Output can be displayed in an interactive updating display or in batch mode for scripting.

Common features include filtering to show only processes that are performing I/O, showing per-thread I/O instead of per-process, sorting by read, write, or I/O wait, and controlling the update interval and the number of samples. It relies on root access to read the /proc filesystem and may report incomplete data for processes with short lifetimes or in containers with restricted namespaces.

Installation is available in most distribution repositories and can be installed with the system package manager. For example, apt install iotop on Debian-based systems, yum or dnf install iotop on Red Hat-based systems, or pacman -S iotop on Arch Linux. Typical usage includes running with elevated privileges to monitor all processes, using options to show only active I/O, to display per-thread data, and to run in batch mode for logs.

See also: iostat, pidstat, and other system monitoring tools.