Installing OPNsense 25.1 on a Mini PC: A Complete Step-by-Step Guide

Last updated: 2025-06-16
Applies to: All x86-based Mini PCs with dual Ethernet ports (e.g. Beelink, Qotom, Topton)
Difficulty: Beginner to Intermediate
Tags: Firewall, Homelab, Networking, OPNsense, Open Source

🧭 Purpose

This guide explains how to install OPNsense, a powerful open-source firewall and router platform, onto a small form-factor mini PC. The goal is to help anyone—from curious newcomers to seasoned sysadmins—get their own secure network gateway up and running with confidence.

🔍 What You'll Learn

• How to flash and install OPNsense on a mini PC
• How to set up basic networking (LAN & WAN)
• How to access the web interface for configuration
• Best practices for securing and maintaining your OPNsense box

👤 Who This Is For

This guide is for:

• Beginners building their first home firewall
• Homelab enthusiasts upgrading from consumer routers
• Professionals looking for a lightweight, reliable edge firewall

No prior experience with BSD or OPNsense is required.

✅ What You’ll Need

🛠️ Step 1: Create the OPNsense USB Installer

Before you can install OPNsense, you’ll need to write its image to a USB stick.

🔧 Option A: Windows (with Rufus 4.8.2253)

1. Download Rufus and open it.
2. Insert a USB flash drive (4GB or larger).
3. Download the OPNsense image:
   • Architecture: amd64
   • Image type: VGA
   • Format: .img
4. In Rufus:
   • Device: select your USB stick
   • Boot selection: click SELECT and choose the .img file
   • Image option: will auto-set; accept defaults
   • Partition scheme: MBR
   • File system: FAT32
5. Click Start. If prompted, choose DD Image mode.
6. Once complete, eject the USB safely.

⚠️ Rufus may show warnings about the .img format. If it fails, try Etcher.

🧰 Option B: macOS / Linux / Cross-Platform (Etcher)

1. Download Balena Etcher
2. Open Etcher:
   • Click Flash from file → select your OPNsense .img
   • Select your USB drive
   • Click Flash
3. Eject the USB when done.

🧬 Step 2: Boot Into the Live Environment

Now you're ready to boot your mini PC and install OPNsense.

🔌 1. Connect Your Hardware

• Insert the OPNsense USB drive
• Connect a keyboard and monitor
• Power on the mini PC

⏳ 2. Wait for OPNsense to Boot

Most mini PCs will automatically boot into “live mode” without showing a menu. You’ll see startup messages on screen.

Eventually, you’ll see this message:

Welcome! OPNsense is running in live mode from install media. Please login as 'root' to continue in live mode, or as 'installer' to start the installation. Use the default or previously-imported root password for both accounts. Remote login via SSH is also enabled.

🧑‍💻 3. Start the Installer Manually

1. At the prompt, log in:
   • Username: root
   • Password: Opnsense
2. Now you can have a look around and decide if you still want to proceed; If you have decided that you want to go ahead, continue with step 3.
3. Open the shell by pressing: 8
4. Now type:

opnsense-installer

3. Press Enter and follow the guided installer.

💽 Step 3: Install OPNsense

Inside the installer:

• Keyboard layout: Use default or select yours

🧠 Choosing Between UFS and ZFS (During Install)

During the installation process, you’ll be asked to choose a filesystem. You’ll usually see two options:

🧰 UFS – Unix File System (Recommended for Most)

• ✅ Easier to install and manage
• ✅ Uses less memory (ideal for mini PCs with <8 GB RAM)
• ✅ Fast and reliable for firewall tasks
• ❌ No native snapshot, compression, or data healing
• ❌ Cannot span multiple disks

Use UFS if you:

• Want something simple that "just works"
• Are new to BSD or firewall appliances
• Don’t plan on doing advanced storage or backups within OPNsense

🧪 ZFS – Zettabyte File System (Advanced)

• ✅ Supports snapshots, self-healing, compression
• ✅ Great for RAID setups (mirror, RAIDZ)
• ✅ Designed for enterprise-grade reliability
• ❌ Requires more RAM (minimum 4GB, ideally 8GB+)
• ❌ Slower on boot for low-power devices
• ❌ More complex to manage

Use ZFS if you:

• Want rollback and snapshot features
• Have ≥8 GB RAM and a modern CPU
• Are using multiple disks and want ZFS mirroring

🏁 Quick Recommendation

ℹ️ Tip: If you’re unsure, choose UFS. You can always reinstall later with ZFS if your needs change.

Since my MiniPC has 16GB of RAM, I'll be choosing ZFS.

🧭 Step-by-Step: ZFS Configuration in the OPNsense Installer

If you chose ZFS as your filesystem, follow these steps during install if you also have a single drive:

1. ZFS Configuration Menu

• Select: Install
• Choose: ZFS when prompted for filesystem type

2. Virtual Device Type

• Choose: stripe
  ✔️ This is correct for a single SSD — no redundancy, just performance and ZFS features

3. Install Target Disk

• Select your main drive by pressing the space bar so it has a * next to your chosen drive (e.g., nda0,ada0, nvme0).
  ❗ Double-check the disk size matches your internal drive
  ❌ Do not select your USB install media if that appears.
• Then select Yes to confirm your selection then it will install OPNsense.

🔐 Set the Root Password

You’ll now be asked to **set the root password** for your OPNsense system. This is the password you’ll use:

- At the console login

- To access the Web UI https://192.168.1.1

✅ Choose a strong password. You can change it later through the UI if needed.

Once you have changed the password, select Complete Install then Reboot now.

🧠 The installer may not show options like partition scheme, swap, or 4K alignment when using ZFS on a single disk. These are automatically applied based on best practices for most systems.

🌍 Step 4: Access the Web Interface

1. Plug a laptop or PC into the LAN port
2. Open a browser and go to:https://192.168.1.1
3. Login with:
   • Username: root
   • Password: (the one you set)

Ignore the security warning about the HTTPS certificate—it’s safe.

✅ Step 5: First-Time Configuration (Wizard)

The Web UI wizard will guide you through:

• Hostname, domain, DNS
• WAN type (DHCP, PPPoE, Static)
• LAN IP (change from default if needed)
• Time zone and NTP
• Admin password (optional change)

Follow this guide if you are like me and you have a BT or EE ISP.

How to Replace Your BT or EE Smart Hub with OPNsense (FTTP Setup)

If you’re on BT or EE’s Full Fibre (FTTP) service and want to ditch the locked-down Smart Hub in favour of OPNsense, this guide walks you through a complete setup. It covers everything from physical connections to PPPoE credentials and firewall rules — with no fluff, just practical implementation. ✨ Overview Goal:

theDev.ukJohn Jestin

📚 Resources

• 🔗 OPNsense Docs
• 🔗 Etcher
• 🔗 Rufus
• 🔗 OPNsense Community Forum

🎯 What’s Next?

Once you’re installed and online:

• Create VLANs for IoT / Guest traffic
• Add WireGuard for remote access
• Enable Intrusion Detection (Suricata)
• Integrate with logging tools like Wazuh or Grafana

💬 Need help or want to share your setup?
Join the community at TheDev.uk or post in the comments.