Linux Command: iotop
Real-time I/O usage per process — the "top" for disk activity
Terminal — Performance & Debugging
Command
$
iotop -oPa
Output
Total DISK READ: 0.00 B/s | Total DISK WRITE: 12.45 M/s
PID USER DISK READ DISK WRITE COMMAND
1847 postgres 0 B 1.2 GB postgres: writer
iotop shows which processes are hammering your disks. Flags: -o (only active), -P (processes not threads), -a (accumulated totals). Complements top/htop (CPU/memory) when I/O is the bottleneck — common with databases and log-heavy workloads.