Why Linux Matters: Practice Exercises

6 minute read

These exercises reinforce the concepts from Chapter 3. They range from research and exploration tasks to hands-on shell practice.

Exercise 1 — Research: Linux in Your Favourite CI/CD Tool

Difficulty: ⭐ Easy

Look up the documentation for one of these CI/CD platforms and answer the questions below:

  • GitHub Actions
  • GitLab CI/CD
  • Jenkins
  • CircleCI

Tasks:

  1. Find what the default runner/agent operating system is for jobs
  2. Find the command to print the OS version in a CI job (uname -a or cat /etc/os-release)
  3. Write a minimal CI configuration file (.github/workflows/main.yml or .gitlab-ci.yml) that:
    • Runs on the platform’s default Linux runner
    • Prints uname -a
    • Prints the current user with whoami
💡 Show Answer (GitHub Actions Example) 
# .github/workflows/linux-check.yml
name: Linux Check

on: [push]

jobs:
  check:
    runs-on: ubuntu-22.04       # Ubuntu Linux — the default GitHub Actions runner

    steps:
      - name: Checkout code
        uses: actions/checkout@v4

      - name: Print OS info
        run: uname -a
        # Expected output:
        # Linux runner-name 5.15.0-1052-aws #58~20.04.1-Ubuntu SMP Mon May 20 ...

      - name: Print current user
        run: whoami
        # Expected output:
        # runner

GitLab CI equivalent:

# .gitlab-ci.yml
linux-check:
  image: ubuntu:22.04
  script:
    - uname -a
    - whoami

Key takeaway: GitHub Actions defaults to ubuntu-22.04. GitLab CI uses a Docker image (which is Linux). Both environments are Linux.

Exercise 2 — Cron Scheduling

Difficulty: ⭐⭐ Medium

Write the cron expressions for the following schedules:

  1. Every day at midnight (00:00)
  2. Every Monday at 8:00 AM
  3. Every 15 minutes
  4. On the 1st day of every month at 6:00 AM
  5. At 23:59 on December 31st every year

Then, write a simple shell script that:

  • Appends the current date and time to /tmp/cron-test.log
  • Schedule it to run every minute using crontab
💡 Show Answer

Cron expressions:

# 1. Every day at midnight
0 0 * * *

# 2. Every Monday at 8:00 AM
0 8 * * 1

# 3. Every 15 minutes
*/15 * * * *

# 4. On the 1st of every month at 6:00 AM
0 6 1 * *

# 5. At 23:59 on December 31st every year
59 23 31 12 *

Shell script:

#!/usr/bin/env bash
# /home/ubuntu/scripts/cron-test.sh

echo "$(date '+%Y-%m-%d %H:%M:%S') - cron ran successfully" >> /tmp/cron-test.log

# Make executable
chmod +x /home/ubuntu/scripts/cron-test.sh

# Add to crontab
crontab -e
# Add this line:
* * * * * /home/ubuntu/scripts/cron-test.sh

# Verify after 2 minutes
cat /tmp/cron-test.log
# 2025-04-01 10:01:01 - cron ran successfully
# 2025-04-01 10:02:01 - cron ran successfully

# Remove the cron job when done
crontab -e
# Delete the line you added

Exercise 3 — Package Manager Exploration

Difficulty: ⭐⭐ Medium

Using your system’s package manager (apt, dnf, or brew):

  1. Search for the htop package and find its description
  2. Install htop if it isn’t already installed
  3. Run htop — press q to quit
  4. Find out which package provides the dig command
  5. Install the package that provides dig and run: dig google.com +short
💡 Show Answer (Ubuntu/Debian) 
# 1. Search for htop
apt search htop
# htop/jammy 3.0.5-7build2 amd64
#   interactive processes viewer

# 2. Install htop
sudo apt install htop

# 3. Run htop
htop
# Press q to quit

# 4. Find which package provides 'dig'
apt-file search bin/dig
# Or use:
apt search dig | grep -i "dns"
# dnsutils/jammy ... Clients provided with BIND ...

# 5. Install dnsutils and run dig
sudo apt install dnsutils
dig google.com +short
# 142.250.182.46
# (IP address of google.com — yours may differ)

On macOS with Homebrew:

# 1. Search
brew search htop
# ==> Formulae: htop

# 2. Install
brew install htop

# 4. dig is included with macOS — but for the latest:
brew install bind
dig google.com +short

Exercise 4 — Linux vs Windows: Cost Calculator

Difficulty: ⭐⭐ Medium

Calculate the annual cost difference between Linux and Windows Server for a fleet of 50 EC2 t3.large instances running 24/7.

Use these approximate on-demand prices (us-east-1):

  • Linux t3.large: $0.0832/hour
  • Windows t3.large: $0.1392/hour

Answer these questions:

  1. Monthly cost for 50 Linux instances
  2. Monthly cost for 50 Windows instances
  3. Annual savings by choosing Linux
  4. What else, beyond EC2 costs, would you save by choosing Linux?
💡 Show Answer 
# Calculate with bash
python3 - <<'EOF'
linux_hourly = 0.0832
windows_hourly = 0.1392
instances = 50
hours_per_month = 730   # 365 days × 24 hours / 12

linux_monthly = linux_hourly * instances * hours_per_month
windows_monthly = windows_hourly * instances * hours_per_month

linux_annual = linux_monthly * 12
windows_annual = windows_monthly * 12

savings_annual = windows_annual - linux_annual

print(f"Linux monthly:   ${linux_monthly:,.2f}")
print(f"Windows monthly: ${windows_monthly:,.2f}")
print(f"Linux annual:    ${linux_annual:,.2f}")
print(f"Windows annual:  ${windows_annual:,.2f}")
print(f"Annual savings:  ${savings_annual:,.2f}")
EOF

Linux monthly:   $3,036.80
Windows monthly: $5,080.80
Linux annual:    $36,441.60
Windows annual:  $60,969.60
Annual savings:  $24,528.00

Additional savings with Linux (beyond EC2):

  • No Windows Server CAL (Client Access Licences)
  • No SQL Server licences (use PostgreSQL instead)
  • No IIS licences (use nginx/Apache, both free)
  • No Systems Centre / SCCM costs (use Ansible)
  • Lower support costs (larger community, more free resources)

Total additional savings could easily exceed $50,000–$100,000/year for 50 servers when licensing is factored in.

Exercise 5 — Open Source Tool Discovery

Difficulty: ⭐⭐⭐ Challenging

Discover and evaluate three open source Linux tools you have not used before:

Instructions:

  1. Go to https://github.com/agarrharr/awesome-cli-apps or search GitHub for “awesome linux tools”
  2. Pick three tools you haven’t used
  3. For each tool:
    • Find its GitHub repository
    • Note: stars, last commit date, licence, and short description
    • Install it using your package manager (or build from source)
    • Run it and note one useful command
  4. Write a brief comparison: which tool would you use in a real DevOps workflow and why?
💡 Show Answer (Example Selection)

Tool 1: bat — a better cat

# GitHub: https://github.com/sharkdp/bat
# Stars: 47k+ | Active | MIT Licence
# Description: cat clone with syntax highlighting and line numbers

sudo apt install bat        # Ubuntu 22.04+
# or: sudo apt install bat-cat  # on older Ubuntu

# Usage
bat /etc/nginx/nginx.conf   # Shows config with syntax highlighting + line numbers
bat README.md               # Markdown rendered in terminal
bat --plain myfile.txt      # No decorations (like regular cat)

Tool 2: ripgrep (rg) — a faster grep

# GitHub: https://github.com/BurntSushi/ripgrep
# Stars: 47k+ | Active | MIT Licence
# Description: fast grep that respects .gitignore

sudo apt install ripgrep

# Usage
rg "TODO" src/              # Search for TODO in src/ directory recursively
rg -i "error" /var/log/     # Case-insensitive search in logs
rg --type py "def main"     # Search only Python files

Tool 3: fd — a faster find

# GitHub: https://github.com/sharkdp/fd
# Stars: 33k+ | Active | MIT & Apache Licence
# Description: simple, fast alternative to find

sudo apt install fd-find
# On Ubuntu, the binary is 'fdfind', alias it:
alias fd=fdfind

# Usage
fd ".log" /var/log/          # Find all .log files
fd -t f -x wc -l             # Find files and run wc -l on each
fd --changed-within 1d       # Files changed in the last day

Which to use in DevOps:

  • bat → replace cat in day-to-day config file review
  • rg → replace grep -r when searching codebases or log directories
  • fd → replace find for file discovery in large repositories

All three are faster and more ergonomic than their standard equivalents.

Chapter Summary

After completing these exercises you should be able to:

  • ✅ Configure a CI/CD job on a Linux runner
  • ✅ Write and schedule cron jobs for automation
  • ✅ Use your distro’s package manager to search, install, and manage tools
  • ✅ Calculate and understand the cost difference between Linux and Windows cloud instances
  • ✅ Discover, evaluate, and install open source Linux tools
← Back to Open Source Ecosystem Next Chapter → Setup & Environment

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