Linux Process Monitoring

top

# Open the classic realtime process viewer.

top -H

# Display per-thread activity inside top.

top -p 1234

# Focus top on one or more processes.

htop

# Open the interactive ncurses process monitor if installed.

sudo atop

# Capture system-wide resource and per-process metrics.

btop

# Use a modern TUI monitor if available.

pidstat 1 5

# Sample process activity every second for five intervals.

pidstat -u 1 5

# Report CPU utilization by process.

pidstat -r 1 5

# Show RSS and memory faults per process.

pidstat -d 1 5

# Show per-process block I/O activity.

pidstat -t -u 1 5

# Break metrics down to thread level.

vmstat 1 5

# Inspect run queue, context switches, and system pressure.

iostat -xz 1

# Inspect disk pressure while correlating with pidstat or ps output.

pmap -x 1234 | head -40

# Display a process memory map with sizes and permissions.

smem -r | head

# Compare memory usage with PSS if smem is installed.

lsof -p 1234

# Show files, sockets, and descriptors opened by a process.

lsof -c nginx

# Show open files for processes matching a name prefix.

lsof +L1

# Find processes keeping deleted files open and consuming disk.

cat /proc/1234/status

# Inspect status, memory, capabilities, and thread counts.

ss -tulpn

# List listening and connected sockets with owning processes.

ss -tnp state established

# Inspect established connections and owning processes.

lsof -i :5432

# Find which process uses a local port.

fuser -v 5432/tcp

# Show owners of a TCP or UDP port.