Operating Systems Weekly Reports

Week 1: System Planning and Distribution Selection

24/10/2025

System Architecture Diagram

Distribution Selection Justification

After comparing several Linux server distributions, I decided to use Ubuntu Server for my project. I chose Ubuntu because it is stable, easy to configure, and well-documented, which makes it suitable for developing my command-line and remote administration skills. Although Debian is extremely reliable and secure, its slower updates and smaller repositories make it less flexible for experimenting. On the other hand, CentOS is designed more for enterprise environments and has a steeper learning curve. Overall, Ubuntu provides the best balance between usability, support, and performance for a headless SSH-based setup.

Workstation Configuration Decision

The workstation used is my host operating system running on macOS. MacOS provides built in terminal SSH access to the server virtual machine; this method ensures that all administration is performed remotely, and aligning with professional practices. VirtualBox is used to host the server image and isolating it from the host environment.

Network Configuration Documentation

Due to university network restrictions preventing LAN connections over Wi-Fi, I configured my virtual machine to use a NAT network in VirtualBox 7.2.4 instead of a host-only adapter. To enable secure remote administration, I created a port forwarding rule that maps SSH traffic from the host (MacBook) to the guest virtual machine. This forwards connections from 127.0.0.1:2222 on the host to port 22 on the virtual machine, allowing me to connect locally using the command ssh -p 2222 username@127.0.0.1. This approach avoids university network restrictions while maintaining a realistic remote management workflow.

System Specifications

I used the uname, free, df -h, ip addr, lsb_release commands to provide the following specifications.

      # uname -a
      Linux
      
      # free -h
                    total        used        free      shared  buff/cache   available
      Mem:         2001372      246300     1165364        1024      678632     1755072
      Swap:              0           0           0
      
      # df -h
      Filesystem      Size  Used Avail Use% Mounted on
      tmpfs           196M  1.2M  195M   1% /run
      /dev/sda2        24G  2.7G   20G  12% /
      tmpfs           981M     0  981M   0% /dev/shm
      /dev/sda1       1.1G  6.4M  1.0G   1% /boot/efi
      tmpfs           196M  4.0K  196M   1% /run/user/1000
      
      # ip addr
      1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
          inet 127.0.0.1/8 scope host lo
      2: enp0s8: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
          inet 10.0.2.15/24 scope global dynamic enp0s8
      
      # lsb_release -a
      Distributor ID: Ubuntu
      Description:    Ubuntu 22.04 LTS
      

Week 2: Security Planning and Testing Methodology

31/10/2025

Performance Testing Plane

For this phase, I plan to design a performance testing and monitoring approach that ensures my Linux server remains stable and secure during remote administration. I will monitor resource usage using command-line tools such as top, free, and df -h to assess CPU load, memory utilisation, and disk activity. Network responsiveness will be tested using ping and traceroute, while service reliability will be checked through systemctl status ssh and log analysis with journalctl. These results will form the foundation for comparing performance before and after security hardening, helping to identify any negative impact caused by configuration changes. By maintaining a clear testing methodology and consistent monitoring approach, I aim to ensure the system remains efficient, responsive, and secure throughout the deployment.

Security Configuration Checklist

Threat Model

The threat model outlines three seperate security concerns and suggests mitigation strategies for each of them.

• Brute-force SSH attacks: This occurs when an attacker repeatedly attempts to guess login credentials to gain remote access. To prevent this, I disabled root login, reduced the number of allowed authentication attempts, and configured the firewall to restrict repeated SSH connections, significantly lowering the chance of unauthorised access.


• Privilege escalation: This threat involves a regular user gaining administrative access, often through misconfigured permissions or exploitation of vulnerabilities. I mitigated this by enforcing the principle of least privilege, creating dedicated non-root user accounts, and carefully controlling sudo access to minimise the risk of elevated privilege misuse.


• Unpatched software vulnerabilities: Outdated packages can be exploited by attackers to compromise system security. To address this, I enabled automatic updates using unattended-upgrades and scheduled periodic manual patch reviews to ensure that the system remains fully updated with the latest security fixes.