Solution to the "no bootable device" error that occurs when a Windows instance is started -

Diagnose and fix the "no bootable device" error caused by missing drivers, inactive partitions, or corrupted boot files on a Windows ECS instance.

Symptom

A Windows ECS instance fails to start and displays the "no bootable device" error.

Note

If the OS fails to start, you can only connect to the instance by using VNC.

Causes

Use instance health diagnostics to identify the cause. The following table lists possible causes and solutions.

Cause	Solution
The disk adapter driver is not installed in the image file.	Install a disk adapter driver
An upper-layer disk filter driver (UpperFilter) exception prevents disk identification.	Remove residual entries for the Windows disk filter driver
The system partition is marked as Inactive.	Set the system partition state to Active
Essential system partition files are corrupted, and the boot mode configuration is invalid.	Reconfigure the boot mode of the Windows operating system
The system partition is too small (less than 100 MB).	The instance was created from a faulty custom image. Re-create the image and use it to Replace an OS (system disk). To create images, see Create Windows image files.
The system partition does not exist on the system disk.
The file system type of the system partition is incorrect.

Solutions

Install a disk adapter driver

Install a disk adapter driver on the instance with an attached repair disk.

Connect to the faulty instance.

On the Diagnostic Result page, click VNC Connection. Enter the Administrator username and password from the diagnostic report to log on to the ECS instance with the repair disk attached. See Connect to an instance by using VNC.
Install the disk adapter driver.

For example, if the mounted drive letter is D and the driver file is in C:\Drivers, run one of the following commands:
- Dism: dism.exe /image:D:\ /Add-Driver /Driver:C:\Drivers /recurse.
- PowerShell: Add-WindowsDriver -Path D:\ -Driver C:\Drivers -Recurse.
On the Instance page, move the pointer over the Fixing state that corresponds to the instance and click Detach Repair Disk.
Restart the instance for the changes to take effect.

See Restart an instance.
Connect to the ECS instance. If the connection succeeds, the issue is resolved.

See Log on to a Windows instance using Workbench.

Remove residual entries for the Windows disk filter driver

Solution 1: Reinstall the filter driver

Contact the filter driver vendor for installation instructions.

Solution 2: Delete the residual entries from the registry

Delete residual entries from the registry of the instance with an attached repair disk.

Important

Registry modifications may affect OS stability and security. Back up your current registry settings before making changes.

Connect to the faulty instance.

On the Diagnostic Result page, click VNC Connection. Enter the Administrator username and password from the diagnostic report to log on to the ECS instance with the repair disk attached. See Connect to an instance by using VNC.
Open the Run dialog box. Enter regedit and click OK to open Registry Editor.
In Registry Editor, select HKEY_LOCAL_MACHINE. Choose File > Load Hive.... Navigate to D:\Windows\System32\config\SYSTEM and click Open. When prompted for a key name, enter OfflineSYSTEM.
Delete the residual UpperFilter value data from HKEY_LOCAL_MACHINE\OfflineSYSTEM\ControlSet001\Control\Class\{4d36e967-e325-11ce-bfc1-08002be10318}. In this example, the value data is test_filter.
On the Instance page, move the pointer over the Fixing state that corresponds to the instance and click Detach Repair Disk.
Start the ECS instance.

See Start an instance.
Connect to the ECS instance. If the connection succeeds, the issue is resolved.

See Log on to a Windows instance using Workbench.

Set the system partition state to Active

Set the system partition state to Active on the instance with an attached repair disk.

Connect to the faulty instance.

On the Diagnostic Result page, click VNC Connection. Enter the Administrator username and password from the diagnostic report to log on to the ECS instance with the repair disk attached. See Connect to an instance by using VNC.
Set the system partition state to Active.

Select one of the following methods. In this example, the faulty OS disk number is 1 and the system partition number is 1.
Use DiskPart to resolve the issue
1. Open the DiskPart window.
  
  Enter diskpart in the search box on the desktop and press Enter, or open Windows PowerShell and run the diskpart command.
2. Select the target disk.
```
select disk 1
```
3. Clear the read-only attribute of the disk.
```
attribute disk clear readonly
```
4. Select the system partition.
```
select partition 1
```
5. Set the system partition state to Active.
```
active
```
Use a PowerShell command to resolve the issue
```
Set-Partition -DiskNumber 1 -PartitionNumber 1 -IsActive $true
```
On the Instance page, move the pointer over the Fixing state that corresponds to the instance and click Detach Repair Disk.
Restart the instance for the changes to take effect.

See Restart an instance.
Connect to the ECS instance. If the connection succeeds, the issue is resolved.

See Log on to a Windows instance using Workbench.

Reconfigure the boot mode of the Windows operating system

Reconfigure the boot mode on the faulty instance with an attached repair disk. In this example, the system partition drive letter is S, and the Windows partition drive letter is C.

Connect to the faulty instance.

On the Diagnostic Result page, click VNC Connection. Enter the Administrator username and password from the diagnostic report to log on to the ECS instance with the repair disk attached. See Connect to an instance by using VNC.
Enable Windows Preinstallation Environment (WinPE) mode and run one of the following BCDboot commands to reconfigure the boot mode:
- Unified Extensible Firmware Interface (UEFI) boot mode
```
bcdboot C:\Windows /s S: /f UEFI
```
- Basic input/output system (BIOS) boot mode
```
bcdboot C:\Windows /s S:
```
Run the following command to view the boot settings:
- UEFI boot mode
```
bcdedit /store S:\EFI\Boot\BCD
```
- BIOS boot mode
```
bcdedit /store S:\Boot\BCD
```
Sample output:
(Optional) If the D disk also runs a Windows OS, specify a boot mode for it.
- UEFI boot mode
```
bcdboot D:\Windows /s S: /d /p /addlast /f UEFI
```
- BIOS boot mode
```
bcdboot D:\Windows /s S: /d /p /addlast
```