Challenge 1: List all files (including hidden ones) in your home directory and sort them by modification time.

🎯 Goal: Understand how to list files and sort them based on their last modification time.

• Command:

    ls -alt
  

• Explanation:

  • ls → List files and directories

  • -a → Show hidden files (files starting with .)

  • -l → Display detailed file information (permissions, owner, size, date modified, etc.)

  • -t → Sort by modification time (newest first)

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Challenge 2: Create a directory named devops_challenge_Day1, navigate into it, and create an empty file named day1.txt.

🎯 Goal: Learn directory and file manipulation.

• Commands:

    mkdir devops_challenge_Day1
    cd devops_challenge_Day1
    touch day1.txt
  

• Explanation:

  • mkdir → Creates a new directory

  • cd → Navigates into that directory

  • touch → Creates an empty file

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Challenge 3: Find total disk usage of /var/log in human-readable format.

🎯 Goal: Learn how to check the disk usage of a specific directory.

• Command:

    du -sh /var/log
  

• Explanation:

  • du → Disk usage command

  • -s → Summarizes total size instead of showing individual files

  • -h → Displays output in a human-readable format (KB, MB, GB)

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Challenge 4: Create a new user called devops_user and add them to the sudo group.

🎯 Goal: Learn how to manage users and grant administrative privileges.

• Commands:

    sudo useradd -m devops_user
    sudo usermod -aG sudo devops_user
  

• Explanation:

  • useradd -m → Creates a new user and assigns a home directory

  • usermod -aG → Adds the user to a specific group (sudo in this case)

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Challenge 5: Create a group called devops_team and add devops_user to that group.

🎯 Goal: Learn how to create user groups and manage group memberships.

• Commands:

    sudo groupadd devops_team
    sudo usermod -aG devops_team devops_user
  

• Explanation:

  • groupadd → Creates a new group

  • usermod -aG → Adds an existing user (devops_user) to the new group (devops_team)

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Challenge 6: Change the permissions of day1.txt to allow only the owner to read and write, but no permissions for others.

🎯 Goal: Understand file permissions and how to modify them using chmod.

• Command:

    chmod 600 day1.txt
  

• Explanation:

  • 600 → Sets file permissions so that:

    • Owner → Read (r) and write (w)

    • Group & Others → No permissions (---)

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Challenge 7: Find all files in /etc modified in the last 7 days.

🎯 Goal: Learn how to search for files based on modification time.

• Command:

    find /etc -type f -mtime -7
  

• Explanation:

  • find → Searches for files

  • -type f → Looks for regular files (not directories)

  • -mtime -7 → Finds files modified in the last 7 days

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Challenge 8: Write a one-liner command to find the most frequently used command in your shell history.

🎯 Goal: Analyze and optimize your command-line usage.

• Command:

    history | awk '{print $2}' | sort | uniq -c | sort -nr | head -5
  

• Explanation:

  • history → Displays a list of previously executed commands

  • awk '{print $2}' → Extracts only the command name (ignores line numbers)

  • sort | uniq -c → Counts occurrences of each command

  • sort -nr → Sorts the list in descending order (most used first)

  • head -5 → Shows the top 5 most frequently used commands

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Topics Covered Today

✅ Basic Shell Commands – Navigating directories (cd), listing files (ls), viewing file contents (cat, touch).
✅ Filesystem Hierarchy – Understanding Linux directory structures (/etc, /var, /home).
✅ File Permissions – Using chmod, ls -l, and learning read, write, execute (rwx).
✅ User & Group Management – Creating users (useradd), modifying groups (usermod, groupadd).
✅ File & Directory Operations – Creating, modifying, and searching files (find, du, ls, awk, sort).
✅ History & Command Usage – Analyzing shell history to improve workflow.