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Lab 4.1 - Process Visualization

Objectives​

By the end of this lab, you will be able to:

  • Visualize processes with ps, top, htop
  • Understand the displayed information
  • Filter and sort processes
  • Monitor processes in real-time

Prerequisites​

  • Ubuntu 24.04 installed
  • Terminal open
  • htop installed (optional but recommended)

Exercise 1: ps (Process Status)​

Step 1: Basic Commands​

# View all processes
ps aux

# View current user's processes
ps

# With more details
ps auxf  # Process tree

# View a specific process
ps aux | grep firefox

Step 2: Useful Options​

# Custom format
ps -eo pid,ppid,cmd,%mem,%cpu --sort=-%mem | head -10

# Processes by user
ps -u $USER

# Processes by PID
ps -p 1

# Processes with tree
pstree
pstree -p  # With PID

Step 3: Analysis​

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

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

# Count processes
ps aux | wc -l

# By user
ps aux | awk '{print $1}' | sort | uniq -c | sort -rn

Exercise 2: top​

Step 1: Basic Usage​

# Launch top
top

# Commands in top:
# - 'q': Quit
# - 'k': Kill a process (enter PID)
# - 'r': Renice a process
# - 'M': Sort by memory
# - 'P': Sort by CPU
# - 'f': Change displayed columns
# - '1': View all CPUs

Step 2: Batch Mode​

# Run top in batch mode (once)
top -bn1 | head -20

# Save to a file
top -bn1 > top-output.txt

# View top processes
top -bn1 | grep -A 20 "PID USER"

Exercise 3: htop (Enhanced)​

Step 1: Installation​

# Install htop
sudo apt update
sudo apt install htop

# Launch
htop

Step 2: htop Features​

# htop offers:
# - Colorful and intuitive interface
# - Arrow key navigation
# - Real-time filtering (F4)
# - Search (F3)
# - Kill processes (F9)
# - Renice (F7/F8)
# - Process tree (F5)

Step 3: Configuration​

# In htop:
# - F2: Setup (configuration)
# - F10: Quit

Exercise 4: Detailed Information​

Step 1: /proc​

# Information about a process (replace PID)
PID=$(pgrep -f firefox | head -1)
echo "PID: $PID"

# Status
cat /proc/$PID/status

# Open files
ls -l /proc/$PID/fd/

# Working directory
readlink /proc/$PID/cwd

# Executable
readlink /proc/$PID/exe

Step 2: lsof (if installed)​

# Install
sudo apt install lsof

# Open files by a process
sudo lsof -p $PID

# Processes using a file
sudo lsof /var/log/syslog

# Network connections
sudo lsof -i

Exercise 5: Real-Time Monitoring​

Step 1: watch​

# Monitor processes
watch -n 1 'ps aux --sort=-%cpu | head -10'

# Monitor a specific process
watch -n 1 'ps -p $PID -o pid,%cpu,%mem,cmd'

Step 2: Monitoring Script​

# Create a script
cat > ~/monitor-processes.sh << 'EOF'
#!/bin/bash
while true; do
    clear
    echo "=== $(date) ==="
    echo
    echo "Top 5 CPU:"
    ps aux --sort=-%cpu | head -6
    echo
    echo "Top 5 Memory:"
    ps aux --sort=-%mem | head -6
    echo
    echo "Total processes: $(ps aux | wc -l)"
    sleep 2
done
EOF

chmod +x ~/monitor-processes.sh
# Run: ./monitor-processes.sh

Exercise 6: Advanced Filtering​

Step 1: By Name​

# Find all processes containing "python"
ps aux | grep python

# Exclude the grep process itself
ps aux | grep python | grep -v grep

# With pgrep
pgrep -a python

Step 2: By User​

# User's processes
ps -u root

# All except root
ps aux | grep -v "^root"

Step 3: By State​

# Running processes
ps aux | grep " R "

# Sleeping processes
ps aux | grep " S "

# Zombie processes
ps aux | grep " Z "

Verification​

Checklist​

Ensure you can:

  • Use ps to view processes
  • Use top for real-time monitoring
  • Use htop (enhanced interface)
  • Filter and sort processes
  • View detailed information (/proc)
  • Monitor in real-time

Reflection Questions​

  1. What is the difference between ps and top?

    • ps: snapshot
    • top: real-time, interactive

  2. What do the process states (R, S, Z) mean?

    • R: Running
    • S: Sleeping
    • Z: Zombie

  3. Why is htop preferred over top?

    • More intuitive interface
    • Easier navigation
    • More visual information

Next Steps​

  • Lab 4.2: Process Control
  • Lab 4.3: Priorities and Nice Values
  • Chapter 4.2: Process Visualization

Lab created on: December 2024 - Tested on Ubuntu 24.04