Hands-on

Demonstrating File/Folder Permissions During Exam Time

1. Linux:

Setting Read-Only Permissions:

chmod 444 /exam_folder/exam_file.txt

Restricting Write Access:

chmod -R 550 /exam_folder/

Setting ACLs for Limited Access:

setfacl -m u:student:r /exam_folder/exam_file.txt
setfacl -m u:teacher:rw /exam_folder/exam_file.txt

Locking Files After Exam Time:

chattr +i /exam_folder/exam_file.txt

Troubleshooting ACL Issues in Linux

1. Check If ACL Support Is Enabled

Run:

sudo mount | grep acl

If there’s no output, enable ACL support:

sudo mount -o remount,acl /

For persistent changes, add acl in /etc/fstab:

/dev/sdX  /  ext4  defaults,acl  0  1

Then remount with:

sudo mount -o remount /

2. Verify ACL Package Is Installed

Install ACL if not installed:

sudo apt install acl -y  # Debian/Ubuntu
sudo yum install acl -y  # RHEL/CentOS

3. Check for Invalid Characters in the Command

Try running the command separately, one at a time:

sudo setfacl -m u:student:r-- /home/exam_folder/test.txt
sudo setfacl -m u:teacher:rw- /home/exam_folder/test.txt

4. Verify Users Exist

Check if student and teacher users exist:

getent passwd student
getent passwd teacher

If not, create them:

sudo useradd student
sudo useradd teacher

5. Check If the File Exists

Run:

ls -l /home/exam_folder/test.txt

If it doesn’t exist, create it:

sudo touch /home/exam_folder/test.txt

6. Verify If the File Supports ACLs

Check if the filesystem supports ACLs:

sudo tune2fs -l $(df --output=source /home | tail -1) | grep "Default mount options"

If acl is missing, enable it using tune2fs (for ext4):

sudo tune2fs -o acl /dev/sdX

Replace /dev/sdX with the actual partition name from the previous command.

7. Verify ACLs Applied Successfully

After running the command again, check:

getfacl /home/exam_folder/test.txt

Expected output:

user:student:r--
user:teacher:rw-

2. Windows:

Setting Read-Only Permissions:

1. Right-click the exam folder, select Properties.
2. Navigate to the Security tab.
3. Select Users and click Edit.
4. Check Read & Execute and Deny for Write.
5. Click Apply and OK.

Using Command Line:

icacls C:\exam_folder\exam_file.txt /deny Everyone:(W)

Restricting File Copying:

• Use Group Policy Editor (gpedit.msc) to disable clipboard and USB access during exam time.

Locking Files After Exam:

attrib +R +S +H C:\exam_folder\exam_file.txt

By implementing these measures, the intranet-based exam storage system will ensure security, integrity, and controlled access, preventing data breaches and unauthorized modifications.