Configure Linux users, groups, and file permissions using chmod, chown, and ACLs.
sudo useradd -m labuser2
echo 'SECRET DATA' | sudo tee /home/student/confidential.txt
sudo chmod 600 /home/student/confidential.txt
ls -la /home/student/confidential.txt
sudo -u labuser2 cat /home/student/confidential.txt
sudo visudo
What is the difference between chmod 644, 600, and 755? When would you use each?