Linux Process Management: A Complete Guide for Server Administrators

Viewing Processes

ps aux               # All processes with details
ps aux | grep nginx  # Find specific process
top                  # Interactive real-time view
htop                 # Better interactive viewer (install first)
pgrep nginx          # Get PID by name

Controlling Processes

kill PID             # SIGTERM (graceful)
kill -9 PID          # SIGKILL (force quit)
killall nginx        # Kill by name
pkill -u www-data    # Kill all processes by user

# Adjust priority
renice -n 10 -p PID  # Lower priority (nice 10)
renice -n -5 -p PID  # Higher priority (nice -5, requires root)

systemd Service Management

systemctl start nginx       # Start service
systemctl stop nginx        # Stop service
systemctl restart nginx     # Restart
systemctl reload nginx      # Reload config without restart
systemctl enable nginx      # Start on boot
systemctl status nginx      # Check status and recent logs
journalctl -u nginx -n 100  # View last 100 log lines

FAQ

What is a zombie process?

A zombie process has finished executing but its parent hasn't read its exit status. It appears as Z in ps output. Zombies don't consume CPU or RAM but do occupy a process table entry. They are resolved by fixing the parent process or killing the parent.