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'
My Mini-Exercises
Created a file, messed around with
chmod
andchown
.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.
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
, andchgrp
(needed this more than once today!).
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!
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