Systemd on My IT Journal

GRUB Security Lab: Boot-Time Privilege Escalation & Hardening

Thu, 11 Jun 2026 00:00:00 +0000

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

USB Automounting with systemd

Sat, 06 Jun 2026 00:00:00 +0000

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:

DNS Lab - Dnsmasq, Client resolver, Caching

Tue, 05 May 2026 00:00:00 +0000

🧪 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]

Systemd Restart Behavior: Why Restart=on-failure Didn't Work

Tue, 14 Apr 2026 00:00:00 +0000

🧪 Systemd Service Restart Behavior Lab

📌 Objective

To test and understand how systemd handles automatic service restarts using the Restart=on-failure policy.

⚙️ Environment

OS: Ubuntu (systemd-based)
Tools: systemctl, journalctl, bash

🛠️ Setup

1. Create a test script

sudo nano /usr/local/bin/labtest.sh

#!/bin/bash
while true; do
	echo "lab service is alive: $(date)"
	sleep 10
done

Make it executable:

sudo chmod +x /usr/local/bin/labtest.sh

2. Create a system service

sudo nano /etc/systemd/system/labtest.service

[Unit]
Description=Lab test service
After=network.target

[Service]
ExecStart=/usr/local/bin/labtest.sh
Restart=on-failure
StandardOutput=journal

[Install]
WantedBy=multi-user.target

Step 3 — Start the service

sudo systemctl daemon-reload
sudo systemctl enable labtest
sudo systemctl start labtest
systemctl status labtest