How to Fix Windows Server 2012 R2 Boot Loop without Reinstalling

Error: Windows Server 2012 R2 boot loop

It is not rare to encounter a Server 2012 boot loop and the specific situation of boot cycle can be widely different: “your machine can run into reboot loop with a “We couldn’t complete the updates” message after update”, “it may always boot into blue “Choose an Option” screen”, “it could catch in reboot loop with BSOD like Your PC ran into a Problem, and now restart with an error code”. Whatever the case may be, it is a vexing problem.

What causes the Server 2012 R2 boot loop issue?

It is not uncommon to encounter boot loops in Server 2012 (R2), and the specific characteristics of these loops exhibit considerable diversity. Your system may find itself in a post-update loop, displaying the frustrating message "We were unable to complete the update". Alternatively, it may always boot to a "Select an Option" blue screen, or worse, get stuck in a reboot cycle that appears to be resolving computer issues and reboots with an error code. The manifestations may be different, but the inconvenience remains.

To troubleshoot Windows Server 2012 (R2) boot loop issues, it's important to drill down into the underlying causes:

▪ Update failure.
▪ Corrupted RAM sticks.
▪ Outdated drivers.
▪ Bad Registry entries.
▪ Hard drive issues...

Five fixes for recovering Windows Server 2012 R2 boot loop

The reasons for Server 2012 R2 endless boot loop are complicated and different. To fix this issue, you can unplug all peripheral devices, roll back drivers, or disable Automatic Restart at first. If boot failure still exists, you may need to access Command Prompt and then revert pending updates, restore the system registry, scan system files, rebuild BCD, or do something else.

To access Command Prompt:

1. Insert Windows Server 2012 R2 installation CD/DVD into the machine and boot from it by changing boot drive in BIOS.

2. Press a key when “Press any key to start from CD or DVD” prompts.

3. Choose a language to install, time and currency format, keyboard or input methods, and click "Next".

4. Choose "Repair your computer" and Windows Server 2012 R2. Then, click “Next”.

5. In the System Recovery Options window, choose “Command Prompt”.

After entering Command Prompt, you can try one or more measures presented in the following text based on your own situation.

✔ Fix 1. Run DISM command to revert pending updates

When Windows Server 2012 R2 hangs on boot after update and shows errors like “We couldn’t complete the updates. Undoing changes. Don’t turn off your computer”, you can revert pending updates to fix the error by running the following commands:

● mkdir c:\scratch (This command is used to create a new directory called Scratch)
● dism /image:c:\ /scratchdir:c:\scratch /cleanup-image /revertpendingactions

PS.: “c” is the drive letter of the drive that holds “Windows” folder. You can change it according to your own case.

After reverting, exit from Command Prompt and restart your machine from system hard drive.

✔ Fix 2. Restore bad registry from Regback

If the Windows Server 2012 boot issue is related with missing or corrupted system registry files, follow steps below to restore system registry files from backup.

1. Confirm your system drive. For example, if you aren’t sure about whether C is your system drive, you can run “dir c:” to see whether there is Progam Files, Users and etc.

2. Type “copy c:windowssystem32configRegBack* d:windowssystem32config” and hit Enter.

Notes:
▪ If the drive letter of your system drive is not c, replace “c” with the corresponding drive letter.
▪ When the registry backup is too old, this way may not be working.

✔ Fix 3. Scan and replace corrupted system files.

If the endless reboot has nothing with update failure or system registry files, consider scanning the integrity of all protected system files and repairing the incorrect by typing the command “sfc/scannow” and hitting Enter.

✔ Fix 4. Check boot volume and fix errors

There are chances that Server 2012 not booting smoothly with BOSD is caused by corrupted boot volume. To scan and fix errors on boot volume, you can type “chkdsk c:/f/r” and hit Enter key. When you prompted by “Chkdsk cannot run because the volume is in use by … Would you like to force a dismount on this volume? (Y/N)”, type “y” and hit Enter key.

✔ Fix 5. Run Bootrec.exes to repair MBR

In many cases, boot failure occurs due to corrupted MBR. To scan and repair it, you can run the commands given below:

▪ bootrec.exe /fixmbr (This command fixes MBR by writing a new Windows-compatible MBR but will not overwrite the existing partition table )
▪ bootrec.exe /fixboot (It writes a new boot sector on the hard disk if Windows detect damage)
▪ bootrec.exe /scanos (It scans your operating system)
▪ bootrec.exe /rebuildbcd (This command rebuilds BCD (Boot Configuration Data) that contains boot information and partition parameters.)

✔ Fix 6. Uninstall update

Microsoft released the Windows Server 2012 R2 KB5009624 update, installing this update will cause your Server 2012 domain controller boot in loops. And the update also affects the Hyper-V servers and most admins have observed the Hyper-V not starting, and inaccessible ReFS volumes until the updates are rolled back. 

You can try to boot from the installation media, then, open CMD and use command lines to uninstall specific updates:

1. Insert your installation media and re-start the system.

2. Boot into your installation media and select Repair your computer.

3. Advance Startup Options – Command Prompt.

4. Enter “wusa /uninstall /kb:4093123” and end with enter.

If you can successfully uninstall the update, remove the installation medium, and try to restart the system in moral mode.

How to fix Server 2012 R2 without a Windows installation disc

When you have Windows Server 2012 R2 installation CD/DVD at hand, you can go to Command Prompt to run different commands for repairing the boot issue. But when there is no Windows installation disc, what should you do?

Don’t worry, here will introduce a powerful and reliable third-party GUI tool for Windows Server 2012 R2, AOMEI Partition Assistant Server. You can use it to create a Windows 11 bootable USB and boot your machine from the created bootable media to check system disk and rebuild MBR. It is with a user-friendly interface, making it fairly simple to use. Then, have a look at how it works.

You can download the Demo version of AOMEI Partition Assistant Server to see how to fix the Server 2012 R2 boot loop.

Before you repair Windows Server 2012 R2:
1. Connect a USB to a working computer, install and run AOMEI Partition Assistant Server on the computer
2. Go to Make Bootable Media > USB Boot Device and then follow its prompt to complete the whole process
3. Insert the bootable USB to the computer whose Windows Server 2012 R2 needs repairing and enter BIOS to boot from the bootable USB.

After booting successfully from the created bootable device via AOMEI Partition Assistant Server, you’ll be in the main interface of the software automatically. Then, you can rebuild MBR or check bad sectors.

✔ Rebuild MBR via AOMEI Partition Assistant Server

Step 1. In the main console, right-click the system hard drive and choose Rebuild MBR.

Step 2. Choose the third one on the drop-down menu. And then click OK.

Step 3. In the main interface, click Apply and Proceed to commit operation.

✔ Check and fix errors for system drive

Step 1. Right-click the system partition (here is partition C) and go to Advanced >Check Partition.

Step 2. In the pop-up window, choose Check partition and fix errors in this partition by using chkdsk.exe and click OK.

Step 3. Wait for the operation to finish.

★Tips:

▪This software is compatible with Windows Server 2022/2019/2016/2012(R2)/2008 (R2)/2003, etc.

▪ Apart from the functions aforementioned, it allows you to make partition recovery, convert MBR disk into GPT without data loss, and more.

▪ To install AOMEI Partition Assistant on unlimited PCs within one company, AOMEI Partition Assistant Unlimited is recommended. And Unlimited edition has a powerful function, "Create Portable Version", enabling you to create AOMEI Partition Assistant to a removable device, like a USB drive. 

▪ If any data loss happens during your operation, you can use the "Recover Data" function to retrieve lost data.

Final words

Now you have realized how to deal with Windows Server 2012 R2 boot loop problem. But you cannot recover your operating system all the time. Therefore, it is recommended to clone Windows Server 2012 R2 disk as a backup or back up operating system in advance.