Linux File Permissions

Explain Linux file permissions. What does the permission 'rwxr-xr--' mean?

Linuxbeginner

// interview question

Explain Linux file permissions. What does the permission 'rwxr-xr--' mean?

Sample answer

Linux file permissions are divided into three groups: owner, group, and others. Each has read (r), write (w), and execute (x) permissions. 'rwxr-xr--' means: owner has full access (rwx), group can read and execute (r-x), others can only read (r--). Use chmod to modify permissions and chown to change ownership.

Why this matters

File permissions are fundamental to Linux security. They control who can read, write, or execute files. Understanding permissions is essential for troubleshooting access issues, setting up secure deployments, and managing shared resources in team environments.

Code examples

View and modify permissions

bash

# View file permissions
ls -la myfile.sh
# Output: -rwxr-xr-- 1 devops team 1234 Dec 1 10:00 myfile.sh

# Make file executable
chmod +x script.sh

# Set specific permissions (owner: rwx, group: rx, others: r)
chmod 754 script.sh

# Recursive permission change
chmod -R 755 /var/www/html/

Change ownership

bash

# Change owner
chown newuser myfile.txt

# Change owner and group
chown newuser:newgroup myfile.txt

# Recursive ownership change
chown -R www-data:www-data /var/www/

Common mistakes to avoid

Setting chmod 777 on production files (security risk)
Forgetting that directories need execute permission for traversal
Not understanding the difference between numeric and symbolic notation

Likely follow-ups

What is the difference between chmod 755 and chmod 777?
How do special permissions like setuid, setgid, and sticky bit work?
What is umask and how does it affect default file permissions?

Answer out loud first, then check yourself against the model answer.

Practice all Junior questions More Linux questions

#linux#permissions#security#fundamentals#sysadmin

Also worth your time on this topic

Article

How to Change File and Folder Permissions Recursively in Linux

Learn how to use chmod command to change permissions for directories and all their subdirectories and files efficiently and safely.

Interview

Environment Variables

What are environment variables and how do you use them in Linux? How do you make them persistent?

junior

Exercise

Securing Your Linux Server: Essential First Steps

Harden a fresh Ubuntu 24.04 server by creating a non-root user, locking down SSH, configuring a firewall with UFW, and setting up fail2ban to block brute-force attacks.

45 minutes

Linux File Permissions

More Linux interview questions

Also worth your time on this topic

How to Change File and Folder Permissions Recursively in Linux

Environment Variables

Securing Your Linux Server: Essential First Steps