Sysadmin

Objective The lab focuses on troubleshooting real-world network failures by systematically isolating issues at each layer of the network stack. Network Topology LAN (User Network) DMZ (Service Network) 192.168.10.0/24 192.168.20.0/24 __________________ _____________________ Client VM Server VM 192.168.10.101 192.168.20.10 | | | | ________ Firewall VM ___________ (Router + Firewall) Issue 1: No connectivity between networks Failure to connect to the webserver Troubleshooting Workflow Step 1 - Verify the service exists From Server: ...

Objective The goal of this lab is to design and implement a basic DMZ (Demilitarized Zone) network using Linux virtual machines, understand routing between network segments, and apply nftables as a stateful firewall. Network Topology LAN (User Network) DMZ (Service Network) 192.168.10.0/24 192.168.20.0/24 __________________ _____________________ Client VM Server VM 192.168.10.101 192.168.20.10 | | | | ________ Firewall VM ___________ (Router + Firewall) VM & Routing Configuration Client VM sudo netplan try sudo netplan apply Firewall VM (Core Router) ...

Objective Lab Environment Client VM 1 - 192.168.10.101 Client VM 2 - 192.168.10.102 Server VM - 192.168.10.10 Server Setup Step 1 - Run web server python3 -m http.server 8080 ss -tln | grep :8080 Step 2 - Base firewall configuration sudo nft add table inet filter sudo nft add chain inet filter input \ '{ type filter hook input priority 0; policy drop; }' sudo nft add rule inet filter input iif lo accept sudo nft add rule inet filter input ct state established,related accept ...

Objective This lab demonstrates how Linux Full Disk Encryption (LUKS) works and what it protects against. Part 1 - Attack Scenario (Unencrypted Disk) Step 1 - Identify disk lsblk Step 2 - Create filesystem (no ecnryption) sudo mkfs.ext4 /dev/sdc Step 3 - Mount disk sudo mkdir /mnt/test sudo mount /dev/sdc /mnt/test Step 4 - Add sensitive data echo "Sensitive data" | sudo tee /mount/test/secret.txt ATTACK SIMULATION Step 1 - Direct mount attempt sudo mkdir /mnt/attack; sudo mount /dev/sdc /mnt/attack ls -l /mnt/attack cat /mnt/attack/secret.txt ...

Attack Simulation: Gaining Root Access via GRUB Objective Demonstrate how physical access to a Linux system can be abused to gain root privileges by modifying GRUB boot parameters. Prerequisites OS: Linux Ubuntu Access to GRUB menu during boot No GRUB password protection enabled Attack Steps Reboot the system and access the GRUB menu. Select the default Linux entry and press e to edit boot parameters. Locate the line starting with: linux /boot/vmlinuz-… Modify the line Boot the modified entry using Ctrl + X ...

Objective Setting up automatic USB drive mounting on a Linux server using systemd mount and automount units Environment OS: Ubuntu Tools: system, USB drive Step 1 - Find Partition UUID Prerequisite: Plugin USB drive blkid /dev/sdb1 Note: UUID and filesystem type Step 2 - Create the Mount Unit sudo nano /etc/systemd/system/mnt-usb.mount Step 3 - Create Automount Unit sudo nano /etc/systemd/system/mnt-usb.automount Step 4 - Enable and Start sudo systemctl enable mnt-usb.automount sudo systemctl start mnt-usb.automount Step 5 - Verify and test Check the automount is active: ...

Objective Build a centralized logging environment where: SERVER receives logs from client1 SERVER receives logs from client2 Logs are stored in separate files: /var/log/client1.log /var/log/client2.log Network Layout Host IP server 192.168.10.10 client1 192.168.10.101 client2 192.168.10.102 Environment OS: Ubuntu Tools: rsyslog Part 1 - Configure the rsyslog Server Verify rsyslog sudo systemctl status rsyslog Enable UDP Syslog reception and restart the rsyslog service sudo nano /etc/rsyslog.conf sudo systemctl restart rsyslog ...

🧪 DNS Lab 📌 Objective Understand DNS from a systems perpective ⚙️ Environment Virtualization: VirtualBox OS: ( 1 DNS Server VM + 1 Client VM) 🛠️ Lab Network Topology 🧩 Phase 1 — Direct DNS (No Cache) Client VM -> dnsmasq (192.168.10.10) Used for: Break #1 (Wrong DNS Server) Break #2 (Wrong DNS Record) 🧩 Phase 2 — Direct DNS (No Cache) Clint VM -> systemd-resolved (127.0.0.53) [CACHE] -> dnsmasq (192.168.10.10) [DNS SERVER] ...

🧪 Inter-Interface Packet Forwarding Failure Investigation 📌 Objective Diagnose why a client cannot reach the internet ⚙️ Environment Virtualization: VirtualBox OS: ( 1 DHCP Server VM + 1 Client VM) 🛠️ Lab Network Topology Server (DHCP) IP: 192.168.10.10 Interfaces: enp0s8 -> LAN enp0s3 -> NAT Client VM IP: 192.168.10.100 Interface: enp0s8 Gateway: 192.168.10.10 🚨 Incident Statement Client cannot access the internet 🔍 PHASE 1 — Verify the Problem Run on Client VM: ...

🧪 Process Management & Resource Control Lab 📌 Objective Simulate and troubleshoot a real-world system slowdown caused by CPU saturation and memory exhaustion. ⚙️ Environment Virtualization: VirtualBox OS: Ubuntu Server 🛠️ Lab Setup Step 1 - Create CPU Load Script nano cpu_hog.sh chmod +x cpu_hog.sh Step 2 - Create Memory Load Script (Python) nano mem_hog.py chmod +x mem_hog.py 🚨 Incident Simulation Step 1 - Check the System Load Baseline uptime ...