How to Dual-Boot FreeBSD with Windows Using GRUB on FreeBSD Operating System

Dual-booting FreeBSD and Windows is an excellent way to leverage the strengths of both operating systems. Windows provides a familiar environment for general computing, gaming, and commercial software, while FreeBSD offers a powerful, Unix-like system with a reputation for security, performance, and stability. By using GRUB (Grand Unified Bootloader), you can effectively manage multiple operating systems on a single machine.

In this guide, we will walk you through the step-by-step process of setting up a dual-boot system with FreeBSD and Windows using GRUB as the bootloader.

Prerequisites

Before proceeding, ensure that you have:

• A computer with Windows already installed or planned for installation.
• A FreeBSD installation ISO (downloadable from FreeBSD.org).
• A bootable USB drive or DVD for FreeBSD installation.
• Basic knowledge of partitioning and disk management.
• GRUB bootloader (to be installed on FreeBSD).

Step 1: Install Windows (If Not Already Installed)

Windows should be installed before FreeBSD because it tends to overwrite the bootloader during installation.

1. Create a Bootable Windows USB/DVD:

   • Use Rufus (Windows) or dd command (Linux) to create a bootable USB.
   • Boot from the USB and install Windows as usual.
   • Ensure that Windows is installed in either MBR (BIOS Mode) or GPT (UEFI Mode).

2. Check Windows Partitioning Scheme:

   • Open Disk Management (diskmgmt.msc in Windows).
   • Identify the partitions. Ensure you leave unallocated space for FreeBSD installation.

Step 2: Install FreeBSD

1. Create a Bootable FreeBSD USB/DVD:

   • Use dd or Rufus to write the FreeBSD ISO onto a USB stick.

2. Boot from the FreeBSD Installer:

   • Restart your computer and boot from the USB/DVD.
   • Select the Install FreeBSD option.

3. Partition the Disk for FreeBSD:

   • Use the Guided Disk Setup and choose Manual Partitioning.
   • Create at least two partitions:
     • / (root) – Recommended 20GB or more.
     • Swap – Recommended 2-4GB (or equal to your RAM).
   • Choose UFS or ZFS as your filesystem.
   • Do NOT install the FreeBSD bootloader, as GRUB will be used instead.

4. Complete the Installation:

   • Set the root password and create a user account.
   • Install additional software if needed.
   • Reboot into FreeBSD.

Step 3: Install and Configure GRUB on FreeBSD

Since we did not install the FreeBSD bootloader, we will now install GRUB and configure it to recognize both Windows and FreeBSD.

1. Install GRUB

Log into FreeBSD and install GRUB using the package manager:

pkg install grub2

Or if you are using ports:

cd /usr/ports/sysutils/grub2
make install clean

2. Install GRUB to the Disk

If you are using MBR (Legacy BIOS mode):

grub-install --target=i386-pc /dev/ada0

If you are using UEFI mode:

grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=GRUB

Replace /dev/ada0 with the correct disk identifier.

3. Generate GRUB Configuration

After installing GRUB, generate the GRUB configuration file:

grub-mkconfig -o /boot/grub/grub.cfg

Step 4: Configure GRUB to Dual Boot FreeBSD and Windows

Edit the GRUB configuration file:

nano /boot/grub/grub.cfg

Add FreeBSD Entry

Find the menuentry section and add the following lines:

menuentry "FreeBSD" {
    insmod ufs2
    set root='(hd0,2)'
    chainloader +1
}

Change (hd0,2) to match your FreeBSD partition.

Add Windows Entry

For Windows, add:

menuentry "Windows 10" {
    insmod ntfs
    set root='(hd0,1)'
    chainloader +1
}

Again, ensure (hd0,1) corresponds to the Windows partition.

Save and exit the file (CTRL + X, then Y, then Enter).

Step 5: Set GRUB as the Default Bootloader

To ensure GRUB loads on boot, update the FreeBSD bootloader settings:

echo 'GRUB_ENABLE_BLSCFG=true' >> /etc/default/grub
grub-mkconfig -o /boot/grub/grub.cfg

Finally, reboot the system:

reboot

Step 6: Verify Dual Boot Functionality

1. Upon restarting, you should see the GRUB menu.
2. Select Windows 10 to boot into Windows.
3. Select FreeBSD to boot into FreeBSD.
4. If Windows fails to boot, check if Fast Boot is enabled in BIOS and disable it.

Troubleshooting Tips

1. GRUB Doesn’t Show Up?

• Boot into FreeBSD using a live USB and reinstall GRUB:

grub-install --target=i386-pc /dev/ada0
grub-mkconfig -o /boot/grub/grub.cfg

2. Windows Boot Manager Overwrites GRUB?

• Boot into FreeBSD and reinstall GRUB using the same steps above.
• Disable Secure Boot and Fast Startup in Windows.

3. Incorrect Partition Numbers?

• Use ls (hd0,msdosX)/ in the GRUB command line (c key) to find the correct partition.

Conclusion

By following these steps, you have successfully set up a dual-boot system with FreeBSD and Windows using GRUB. This configuration allows you to leverage the benefits of both operating systems while maintaining a flexible and efficient boot management system.

If you run into issues, FreeBSD’s official handbook and community forums are great resources for troubleshooting.

FAQs

1. Can I use FreeBSD’s bootloader instead of GRUB?

Yes, FreeBSD has its own bootloader (boot0cfg), but GRUB provides more flexibility when managing multiple OS installations.

2. How do I update GRUB if I install another OS?

Run the following command in FreeBSD:

grub-mkconfig -o /boot/grub/grub.cfg

3. What if I don’t see Windows in GRUB?

Ensure the Windows partition is correctly detected using:

lsblk

Manually add the Windows entry in /boot/grub/grub.cfg.

4. Can I install FreeBSD and Windows on separate drives?

Yes, but you may need to configure GRUB to detect both disks by specifying their paths correctly.

5. What happens if Windows updates break GRUB?

Simply boot into a FreeBSD live USB and reinstall GRUB.

6. Is dual-booting FreeBSD and Windows safe?

Yes, as long as you partition your disk correctly and avoid formatting the wrong partitions.

By following this guide, you now have a robust dual-boot system with FreeBSD and Windows managed via GRUB. Enjoy your new setup! 🚀