Linux for DevOps – Part 2: Files, Directories & Permissions Explained Simply

Introduction

In real DevOps work, many problems happen because of wrong file or directory permissions.
You may see errors like:

❌ Permission denied
❌ Script not executable
❌ Jenkins pipeline failed

These issues are not bugs, they are Linux permission problems.

In this blog, we will understand:

• Linux files and directories

• How permissions work

• chmod and chown

• A real DevOps example

All explained in simple English.

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Linux Files and Directories

Linux treats everything as a file.

Common File Types

• Regular file (-) → text files, scripts, logs

• Directory (d) → folders

• Symbolic link (l) → shortcut to another file

You can check file type using:

ls -l

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Basic File and Directory Commands

These commands are used daily by DevOps engineers.

touch file.txt      # Create a file
mkdir logs          # Create a directory
rm file.txt         # Delete a file
cp app.log backup.log   # Copy a file
mv old.txt new.txt  # Rename or move a file

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Understanding Linux Permissions

Every file and directory has three levels of access:

1. Owner – user who owns the file

2. Group – group associated with the file

3. Others – everyone else

Permission Types

• r → read

• w → write

• x → execute

Example:

-rwxr-xr--

Meaning:

• Owner → read, write, execute

• Group → read, execute

• Others → read only

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chmod – Change File Permissions

The chmod command is used to change permissions.

Numeric Method

chmod 755 script.sh

Symbolic Method

chmod +x script.sh

👉 This is very common in DevOps when scripts fail to run.

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chown – Change File Ownership

The chown command changes the owner and group of a file.

chown ubuntu:ubuntu file.txt

This means:

• Owner = ubuntu

• Group = ubuntu

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Real DevOps Scenario (Very Important)

Problem:

A Jenkins pipeline fails with this error:

Permission denied

Reason:

Jenkins does not have permission to execute the script.

Solution:

chmod +x deploy.sh
chown jenkins:jenkins deploy.sh

✅ Pipeline works successfully.

This is a real production-level DevOps issue.

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Best Practices for DevOps Engineers

• ❌ Do NOT use chmod 777 in production

• ✅ Give minimum required permissions

• ✅ Use groups for access control

• ✅ Always check permissions before deployment

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Conclusion

Linux permissions are one of the most important DevOps skills.

If you understand:

• Files and directories

• chmod and chown

You can solve most “Permission denied” errors easily.

In the next part, we will learn:
👉 Users, Groups, Processes & Services in Linux