Understanding File Permissions and Ownership in Linux

 Introduction

File permissions in Linux determine who can read, write, or execute files. Understanding this concept is crucial for system security and user management.

Step 1: View File Permissions

Use the ls -l command to list files with their permissions.

ls -l

➡️ Example output:

-rw-r--r-- 1 user group 1234 Sep 18 file.txt

Step 2: Permission Breakdown

r = read

w = write

x = execute

In -rw-r--r--:

First part (rw-) → owner permissions

Second part (r--) → group permissions

Third part (r--) → others permissions

Step 3: Change Permissions with chmod

To add execute permission for the owner:

chmod u+x file.txt

➡️ u = user (owner), g = group, o = others, a = all.

Step 4: Change Ownership with chown

To change the owner of a file:

sudo chown newuser file.txt

➡️ To change both owner and group:

sudo chown newuser:newgroup file.txt

Step 5: Numeric Permissions

You can also set permissions using numbers (octal mode):

4 = read

2 = write

1 = execute

Example:

chmod 755 script.sh

➡️ 755 means: owner = read/write/execute, group = read/execute, others = read/execute.

Conclusion

Mastering file permissions and ownership is key to maintaining a secure Linux environment. In the next post, we’ll dive into process management.