How to Change from Legacy to Eufi on Dell Serve

Switching from Legacy BIOS to UEFI on a Dell server improves boot speed, security, and hardware compatibility. This guide walks you through the entire process—from preparation to post-conversion checks—ensuring a smooth and error-free transition.

Key Takeaways

• Backup your data first: Always create a full system backup before making firmware changes to prevent data loss.
• Check OS compatibility: Ensure your operating system supports UEFI boot mode—most modern OS versions do, but older ones may not.
• Use iDRAC for remote access: Dell’s Integrated Dell Remote Access Controller (iDRAC) lets you manage the server remotely during the conversion.
• Clear Secure Boot keys if needed: You may need to reset or reconfigure Secure Boot settings after switching to UEFI.
• Update firmware beforehand: Running the latest BIOS and iDRAC firmware reduces the risk of errors during the transition.
• Test boot order post-conversion: Verify that the correct boot device is prioritized in UEFI mode to avoid boot failures.
• Have a recovery plan ready: Know how to revert to Legacy mode if issues arise, using BIOS settings or bootable recovery media.

Introduction: Why Switch from Legacy to UEFI on Dell Servers?

If you’re managing a Dell server, you might be wondering whether it’s worth switching from the traditional Legacy BIOS to the newer UEFI (Unified Extensible Firmware Interface) mode. The short answer? Yes—especially if you’re aiming for better performance, enhanced security, and future-proofing your infrastructure.

Legacy BIOS has been around for decades and works reliably, but it has limitations. It can only boot from drives smaller than 2.2TB, lacks modern security features like Secure Boot, and generally boots slower than UEFI. UEFI, on the other hand, supports larger drives, faster boot times, improved hardware initialization, and advanced security protocols. For Dell servers—especially PowerEdge models—UEFI is the recommended firmware interface for modern workloads.

In this comprehensive guide, we’ll walk you through the entire process of changing from Legacy to UEFI mode on a Dell server. Whether you’re using a PowerEdge R740, R650, or an older model like the R720, the steps are similar. We’ll cover preparation, BIOS configuration, OS considerations, troubleshooting, and best practices to ensure a smooth transition.

By the end of this guide, you’ll know exactly how to safely switch your Dell server to UEFI mode—without losing data or disrupting operations.

Understanding Legacy vs. UEFI: What’s the Difference?

Before diving into the conversion process, it’s important to understand what Legacy and UEFI actually mean—and why the shift matters.

Legacy BIOS (Basic Input/Output System) is the traditional firmware interface that has powered computers since the 1980s. It initializes hardware during startup and loads the operating system from a boot device. However, it operates in 16-bit mode, which limits its capabilities. For example, it can’t handle drives larger than 2.2TB using the MBR (Master Boot Record) partitioning scheme, and it lacks support for modern security features.

UEFI, introduced in the early 2000s and now standard on all new Dell servers, is a more advanced firmware interface. It supports 32-bit and 64-bit modes, allowing faster hardware initialization and boot times. UEFI uses the GPT (GUID Partition Table) partitioning scheme, which supports drives larger than 2.2TB. It also includes features like Secure Boot, which prevents unauthorized operating systems and malware from loading during startup.

For Dell servers, UEFI offers several advantages:
– Faster boot and shutdown times
– Support for large-capacity storage drives
– Improved hardware diagnostics and management
– Enhanced security with Secure Boot and TPM integration
– Better compatibility with modern operating systems like Windows Server 2016+, VMware ESXi 6.7+, and Linux distributions with UEFI support

Switching to UEFI isn’t just a technical upgrade—it’s a strategic move toward a more secure, efficient, and scalable server environment.

Preparing for the Legacy to UEFI Conversion

Before you flip the switch in the BIOS, proper preparation is critical. Rushing into the conversion without planning can lead to boot failures, data loss, or system instability. Follow these steps to ensure a safe and successful transition.

Step 1: Backup Your Data

This cannot be stressed enough: always back up your data before making firmware changes. Even though the conversion process doesn’t typically erase data, there’s always a risk of something going wrong—especially if the server fails to boot afterward.

Create a full system image backup using tools like:
– Windows Server Backup (for Windows environments)
– Acronis True Image or Veeam for physical servers
– Clonezilla for Linux-based systems

Store the backup on an external drive or network location. Verify the backup by testing a restore on a non-production machine if possible.

Step 2: Verify Operating System Compatibility

Not all operating systems support UEFI boot mode. Check your OS version to ensure compatibility:

– Windows Server: Windows Server 2012 and later support UEFI. Earlier versions (2008 R2 and below) may require Legacy mode.
– Linux: Most modern distributions (Ubuntu 16.04+, CentOS 7+, RHEL 7+) support UEFI. Check your distribution’s documentation.
– VMware ESXi: ESXi 6.5 and later support UEFI. Earlier versions may not.

If your OS doesn’t support UEFI, you’ll need to upgrade or reinstall it—preferably on a GPT-partitioned drive.

Step 3: Update Firmware and Drivers

Outdated firmware can cause compatibility issues during the UEFI transition. Dell regularly releases BIOS and iDRAC updates that improve UEFI stability and performance.

To update:
1. Visit the Dell Support website.
2. Enter your server’s Service Tag or model number.
3. Download the latest BIOS and iDRAC firmware updates.
4. Apply the updates using Dell Update Packages (DUP) or through iDRAC.

Updating firmware reduces the risk of boot errors and ensures your server is running the most stable version of UEFI.

Step 4: Document Current BIOS Settings

Before making changes, take note of your current BIOS configuration. This includes:
– Boot order
– RAID controller settings
– Power management options
– Virtualization settings (Intel VT-x/AMD-V)
– Secure Boot status

You can document these by taking screenshots or writing them down. This will help you restore settings if needed after the conversion.

Step 5: Prepare Bootable Media (Optional but Recommended)

In case the server fails to boot after switching to UEFI, have a bootable USB drive ready with:
– A recovery OS (like Windows PE or a Linux live CD)
– Dell diagnostic tools
– Your OS installation media (in UEFI-compatible format)

Ensure the USB drive is formatted with FAT32 and created using UEFI-compatible tools (e.g., Rufus in “UEFI (non-CSM)” mode).

Accessing the BIOS on a Dell Server

Now that you’re prepared, it’s time to access the BIOS to make the switch. Dell servers use a graphical BIOS interface called UEFI BIOS Setup, which is user-friendly and intuitive.

Method 1: Local Access (Physical Keyboard and Monitor)

1. Power on or restart the Dell server.
2. As the Dell logo appears, press the F2 key repeatedly to enter System Setup (BIOS).
3. Wait for the BIOS interface to load. This may take a few seconds.

Method 2: Remote Access via iDRAC

If you don’t have physical access, use Dell’s iDRAC (Integrated Dell Remote Access Controller):
1. Open a web browser and go to the iDRAC IP address (e.g., https://192.168.1.100).
2. Log in with your iDRAC credentials.
3. Navigate to Virtual Console > Launch Virtual Console.
4. In the virtual console, click the F2 button in the toolbar to send the F2 key to the server.
5. The BIOS setup screen will appear in the virtual console.

Using iDRAC is especially helpful for remote data centers or headless servers.

Changing from Legacy to UEFI Mode

Once you’re in the BIOS, follow these steps to switch from Legacy to UEFI boot mode.

Step 1: Navigate to Boot Settings

1. In the BIOS main menu, use the arrow keys to select Boot Settings.
2. Press Enter to open the Boot Settings menu.

Step 2: Change Boot Mode to UEFI

1. Look for an option labeled Boot Mode or Boot List Option.
2. It will likely be set to Legacy or BIOS.
3. Use the arrow keys to change it to UEFI.
4. Press Enter to confirm.

Note: On some Dell servers, you may see options like “UEFI Only” or “UEFI with CSM.” Choose UEFI Only for full UEFI functionality. CSM (Compatibility Support Module) allows Legacy boot but defeats the purpose of switching.

Step 3: Configure Boot Order

After switching to UEFI, the boot order may reset. You’ll need to reconfigure it:
1. In the Boot Settings menu, select Boot Sequence or Boot Order.
2. Use the +/- keys or drag-and-drop (in newer BIOS versions) to prioritize your boot devices.
3. Ensure your primary OS drive (usually a RAID virtual disk) is at the top.
4. If using a USB or network boot, add those as secondary options.

Tip: UEFI boot devices often have “UEFI:” prefixed to their names (e.g., “UEFI: Windows Boot Manager”). Make sure you’re selecting the UEFI version of your boot device.

Step 4: Enable Secure Boot (Optional but Recommended)

Secure Boot is a UEFI feature that ensures only trusted software can load during startup. It’s highly recommended for security:
1. In the BIOS, go to System Security or Secure Boot.
2. Set Secure Boot to Enabled.
3. Choose the appropriate Secure Boot mode:
– Deployed Mode: Full security (recommended for production)
– Audit Mode: Logs unsigned components but doesn’t block them (useful for testing)

Note: If your OS doesn’t support Secure Boot, you may need to disable it temporarily or install signed bootloaders.

Step 5: Save and Exit

1. Press F10 to save changes and exit.
2. Confirm when prompted.
3. The server will reboot automatically.

Post-Conversion Steps and Verification

After the server reboots, it’s time to verify that the conversion was successful and everything is working as expected.

Step 1: Confirm UEFI Mode is Active

To verify the server is now in UEFI mode:
1. Reboot and press F2 to enter BIOS.
2. Go to System Information or Main.
3. Look for “Boot Mode” or “System BIOS Mode.” It should now read UEFI.

Alternatively, in Windows, open Command Prompt as Administrator and run:

bcdedit /enum firmware

If the output shows “UEFI,” the system is in UEFI mode.

In Linux, check with:

ls /sys/firmware/efi

If the directory exists, UEFI is active.

Step 2: Check Boot Performance

One of the benefits of UEFI is faster boot times. Compare the boot duration before and after the switch. You should notice a noticeable improvement, especially on servers with multiple drives or RAID configurations.

Step 3: Verify OS and Application Functionality

Log into the operating system and ensure:
– All services are running
– Network connectivity is intact
– Storage devices are accessible
– Applications launch without errors

Run a quick system health check using Dell OpenManage Server Administrator (OMSA) or your preferred monitoring tool.

Step 4: Update Boot Configuration (If Needed)

In some cases, the OS may not automatically adapt to UEFI mode. You may need to rebuild the boot configuration:

– Windows: Use the bcdboot command to recreate the UEFI boot files:

bcdboot C:\Windows /s S: /f UEFI

(Replace C: with your OS drive and S: with the EFI system partition.)

– Linux: Reinstall GRUB in UEFI mode:

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

Then run update-grub.

Troubleshooting Common Issues

Even with careful preparation, issues can arise. Here are solutions to the most common problems.

Issue 1: Server Won’t Boot After Switching to UEFI

Symptoms: Black screen, “No bootable device” error, or continuous reboot loop.

Solution:
– Re-enter BIOS and confirm Boot Mode is set to UEFI.
– Check that the correct UEFI boot device is selected in the boot order.
– If the OS drive isn’t listed, it may not be UEFI-compatible. You may need to reinstall the OS in UEFI mode.
– Use a bootable USB with recovery tools to repair the bootloader.

Issue 2: Secure Boot Prevents OS from Loading

Symptoms: “Secure Boot Violation” or “Invalid signature” error.

Solution:
– Temporarily disable Secure Boot in BIOS.
– Boot into the OS and install any missing UEFI-signed drivers or bootloaders.
– Re-enable Secure Boot and test.

Issue 3: RAID Controller Not Detected in UEFI

Symptoms: RAID virtual disk not appearing in boot options.

Solution:
– Ensure the RAID controller firmware is up to date.
– Check that the controller is configured for UEFI boot in its BIOS (accessed via Ctrl+R during startup).
– Rebuild the RAID configuration if necessary.

Issue 4: Network Boot (PXE) Not Working

Symptoms: Server fails to PXE boot in UEFI mode.

Solution:
– Ensure your DHCP and PXE servers support UEFI (option 60 should include “PXEClient” and “UEFI”).
– Use UEFI-compatible boot images (e.g., UEFI-capable WinPE or Linux netboot).
– In BIOS, enable “UEFI Network Stack” if available.

Best Practices for Maintaining UEFI Mode

Once your Dell server is successfully running in UEFI mode, follow these best practices to maintain stability and performance:

– Keep firmware updated: Regularly check for BIOS, iDRAC, and driver updates from Dell.
– Monitor Secure Boot logs: Use tools like Windows Event Viewer or Linux audit logs to detect unauthorized boot attempts.
– Document changes: Keep a record of BIOS settings and firmware versions for future reference.
– Test before production: Always test UEFI changes in a non-production environment first.
– Use UEFI-aware tools: When creating bootable media, use tools that support UEFI (e.g., Rufus, Ventoy).

Conclusion: Embrace the Future with UEFI

Switching from Legacy to UEFI on a Dell server is a smart move that unlocks better performance, enhanced security, and greater hardware compatibility. While the process requires careful planning, the benefits far outweigh the risks—especially in modern data centers where speed and security are paramount.

By following this guide, you’ve learned how to safely convert your Dell server to UEFI mode, verify the change, and troubleshoot common issues. Remember: always back up your data, check OS compatibility, and keep firmware updated. With these steps, your server will be ready to handle today’s workloads—and tomorrow’s innovations.

Whether you’re managing a single server or an entire fleet, UEFI is the foundation for a more efficient and secure infrastructure. So go ahead—make the switch, and future-proof your Dell server today.