Why permissions protect system security in Linux CLI - Challenge Your Understanding

Challenge - 5 Problems

💻 Command Output

intermediate

Understanding file permissions with ls -l

What is the output of the command ls -l on a file with permissions -rw-r----- owned by user alice and group staff?

Linux CLI

ls -l example.txt

A drw-r----- 1 alice staff 1234 Apr 27 12:00 example.txt

B -rw-r--r-- 1 alice staff 1234 Apr 27 12:00 example.txt

C -rwxr-xr-x 1 alice staff 1234 Apr 27 12:00 example.txt

D -rw-r----- 1 alice staff 1234 Apr 27 12:00 example.txt

💡 Hint

Look carefully at the permission string and the file type character at the start.

The permission string -rw-r----- means a regular file (-), read and write for owner (rw-), read for group (r--), and no permissions for others (---). The owner is alice and group is staff.

🧠 Conceptual

intermediate

Why do permissions protect system security?

Which of the following best explains why file permissions are important for system security?

A They make files load faster by limiting access.

B They control who can read, write, or execute files, preventing unauthorized access or changes.

C They encrypt files so only certain users can open them.

D They automatically back up files to protect data.

💡 Hint

Think about what permissions actually do to files.

Permissions set who can read, write, or execute files, which helps prevent unauthorized users from accessing or modifying important system files.

🔧 Debug

advanced

Identifying permission error in script

A script tries to write to a file but fails with a 'Permission denied' error. Which command will correctly fix the permission so the script owner can write the file?

Linux CLI

echo 'Hello' > /var/log/app.log

A chmod u+w /var/log/app.log

B chmod o+w /var/log/app.log

C chmod g+w /var/log/app.log

D chmod a-w /var/log/app.log

💡 Hint

The script owner needs write permission, so add write permission to the user.

Adding write permission to the user (owner) with chmod u+w allows the script owner to write to the file. Other options modify group or others or remove write permission.

🚀 Application

advanced

Setting secure permissions for a private directory

You want to create a directory secret that only you can access. Which command sets the correct permissions?

A mkdir secret && chmod 755 secret

B mkdir secret && chmod 777 secret

C mkdir secret && chmod 700 secret

D mkdir secret && chmod 600 secret

💡 Hint

Only the owner should have read, write, and execute permissions.

Permission 700 means only the owner can read, write, and enter the directory. Others have no access. 777 allows everyone access, 755 allows others to read and enter, 600 is invalid for directories because execute permission is needed to enter.

🧠 Conceptual

expert

Effect of removing execute permission on a script

What happens if you remove the execute permission from a shell script file?

A You cannot run the script directly, but you can still read and edit it.

B The script will run faster because it is not executable.

C The script will delete itself automatically.

D The script will run but with limited features.

💡 Hint

Think about what execute permission controls.

Execute permission allows a file to be run as a program. Without it, you cannot run the script directly, but you can still open and edit the file.