Linux User Management and File Permissions Assignment

Introduction

This document outlines the steps taken to create users, configure a system user, grant sudo privileges, and set up a shared directory with advanced group permissions on a Linux Virtual Machine.

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1. Create User: Tupu

I used the adduser script to create the user tupu. This script is interactive and automatically creates the home directory and asks for a password.

Command:

sudo adduser tupu

## 2. Create Lupu User I used the useradd command with specific flags to create the user profile, home directory, and shell. Then I set the password manually.

Commands:

sudo useradd -m -d /home/lupu -s /bin/bash -G lupu lupu
sudo passwd lupu

3. Create Hupu System User

I created a system user named hupu with its login shell set to /bin/false to prevent any interactive login.

Command:

sudo useradd --system --shell /bin/false hupu

4. Grant Sudo Privileges

I added both tupu and lupu to the sudo group to allow them to execute administrative commands.

Commands:

sudo usermod -aG sudo tupu
sudo usermod -aG sudo lupu

5. Directory Permissions and Collaboration (/opt/projekti)

Implementation Explanation To ensure only Tupu and Lupu can access the directory and that all new files maintain the correct group ownership:

Shared Group: I created a group named projekti and added both users to it.

Access Control: I set the permissions to 770 (Full access for Owner/Group, none for others).

SetGID Bit: I applied the setgid bit (chmod g+s). This ensures any file created inside this directory automatically belongs to the projekti group, enabling seamless collaboration.

Commands:

sudo groupadd projekti
sudo usermod -aG projekti tupu
sudo usermod -aG projekti lupu
sudo mkdir -p /opt/projekti
sudo chown :projekti /opt/projekti
sudo chmod 770 /opt/projekti
sudo chmod g+s /opt/projekti

6. Testing and Verification

I verified the configuration by switching to user tupu and creating a file to test the group inheritance (SetGID).

Commands:

su - tupu
cd /opt/projekti
touch verify_test.txt
ls -l

##Result: The output of ls -l confirms that verify_test.txt belongs to the group projekti, proving the permission structure is maintained.