Linux Process Management Deep Dive

Viewing Processes

ps — Snapshot

# All processes with full details
ps aux

# Tree view showing parent-child relationships
ps auxf

# Filter by name
ps aux | grep nginx

htop — Interactive

htop

Key shortcuts in htop:

Process States

Warning D state processes can't be killed — they're waiting for disk I/O. If you see many of these, your disk subsystem may be overloaded.

Signals

# Graceful shutdown (SIGTERM)
kill 1234
kill -15 1234

# Force kill (SIGKILL) — use as last resort
kill -9 1234

# Reload config (SIGHUP)
kill -HUP 1234

# Kill all processes by name
killall nginx
pkill -f "node server.js"

Background Jobs

# Run in background
long-command &

# Suspend foreground process
# Press Ctrl+Z

# Resume in background
bg

# Resume in foreground
fg

# List background jobs
jobs

# Keep running after logout
nohup long-command &
# Or better:
nohup long-command > /var/log/output.log 2>&1 &

Resource Limits with ulimit

# Check current limits
ulimit -a

# Increase open file limit for current session
ulimit -n 65536

# Permanent change in /etc/security/limits.conf
deploy  soft  nofile  65536
deploy  hard  nofile  65536

Finding Resource Hogs

# Top 10 by CPU
ps aux --sort=-%cpu | head -11

# Top 10 by memory
ps aux --sort=-%mem | head -11

# Total memory by process name
ps -eo rss,comm | awk '{arr[$2]+=$1} END {for (i in arr) print arr[i]/1024, "MB", i}' | sort -rn | head -10