DevOps Day 3 - Exploring Linux Permissions & Users

Hey folks! Sharing my Day 3 journey as part of my DevOps learning adventure. Today, I got hands-on with one of the core building blocks for anyone working in backend, automation, or cloud environments: Linux users, groups, and permissions. Here’s how my exploration went—and what I learned!

What I Practiced

Understanding Users & Groups

• Learned that every action on a Linux system happens as a specific user—either a regular user, root, or a service account.

• Groups are just collections of users to help manage permission settings for teams or projects.

Commands I tried:

bashwhoami             # Shows current user
groups             # Lists groups the user belongs to
cut -d: -f1 /etc/passwd   # Quick list of all users

Permissions: The rwx Model

I found out how crucial proper permissions are—not just for security, but also for teamwork. Linux breaks file and folder permissions into three chunks:

• User (owner)

• Group

• Others

And each chunk is represented as:

• r = read (4)

• w = write (2)

• x = execute (1)

For example, -rw-r--r-- means the user can read/write, group and others can only read.

Modifying Permissions and Ownership

chmod – Changing Permissions

bashchmod 755 script.sh      # User can rwx, group/others can rx
chmod o-w secret.txt     # Remove write for others

chown – Changing Ownership

bashsudo chown jayanth myfile.txt   # Set myself as owner

chgrp – Changing Group

bashsudo chgrp devops myfile.txt    # Change group to 'devops'

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My Mini-Exercises

• Created a file, messed around with chmod and chown.

• Made a quick script to practice:

    bashtouch explore.txt
    chmod 600 explore.txt
    sudo chown $USER explore.txt
    ls -l explore.txt
  

  This let me see how only the owner has read/write, and practice switching ownership.

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Reflections & Tips

• Even simple permission mistakes can create big security gaps or block workflows—so always check before changing to 777!

• Knowing which user/group needs access helps me set up safer automation scripts and shared folders.

• Planning to make a quick cheatsheet of chmod, chown, and chgrp (needed this more than once today!).

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What’s Next?

Tomorrow, I’ll be tackling file handling and redirection—using powerful Linux commands to view, filter, and manage output/input. It’s getting more interesting!