Troubleshoot issues with Amazon EC2 Windows instances

Map drive letters to volumes

1. Connect to the instance to configure and open the C:\ProgramData\Amazon\EC2-Windows\Launch\Config\DriveLetterMappingConfig.json file in a text editor.

2. Specify the volume settings as follows:

   {
   "driveLetterMapping": [
   	{
   	  "volumeName": "sample volume",
   	  "driveLetter": "H"
   	}]
   }

3. Save your changes and close the file.

4. Open Windows PowerShell and use the following command to run the EC2Launch v1 script that initializes the disks:

   PS C:\>  C:\ProgramData\Amazon\EC2-Windows\Launch\Scripts\InitializeDisks.ps1

   To initialize the disks each time the instance boots, add the -Schedule flag as follows:

   PS C:\>  C:\ProgramData\Amazon\EC2-Windows\Launch\Scripts\InitializeDisks.ps1 -Schedule

   The EC2Launch v1 agent can run instance initialization scripts such as initializeDisks.ps1 in parallel with the InitializeInstance.ps1 script. If the InitializeInstance.ps1 script reboots the instance, it might interrupt other scheduled tasks that run at instance startup. To avoid any potential conflicts, we recommend that you add logic to your initializeDisks.ps1 script to ensure that instance initialization has finished first.

   Note

   If the EC2Launch script does not initialize the volumes, ensure that the volumes are online. If the volumes are offline, run the following command to bring all disks online.

   PS C:\> Get-Disk | Where-Object IsOffline -Eq $True | Set-Disk -IsOffline $False

To boot an online instance into DSRM using the System Configuration dialog box

1. In the Run dialog box, type msconfig and press Enter.

2. Choose the Boot tab.

3. Under Boot options choose Safe boot.

4. Choose Active Directory repair and then choose OK. The system prompts you to reboot the server.

To boot an offline instance into DSRM

1. Open the Amazon EC2 console at https://console.aws.amazon.com/ec2/.

2. In the navigation pane, choose Instances.

3. Locate and select the affected instance. Choose Instance state, Stop instance.

4. Choose Launch instances and create a temporary instance in the same Availability Zone as the affected instance. Choose an instance type that uses a different version of Windows. For example, if your instance is Windows Server 2016, then choose a Windows Server 2019 instance.

   Important

   If you do not create the instance in the same Availability Zone as the affected instance you will not be able to attach the root volume of the affected instance to the new instance.

5. In the navigation pane, choose Volumes.

6. Locate the root volume of the affected instance. Detach the volume and attach it to the temporary instance you created earlier. Attach it with the default device name (xvdf).

7. Use Remote Desktop to connect to the temporary instance, and then use the Disk Management utility to make the volume available for use.

8. Open a command prompt and run the following command. Replace D with the actual drive letter of the secondary volume you just attached:

   bcdedit /store D:\Boot\BCD /set {default} safeboot dsrepair

9. In the Disk Management Utility, choose the drive you attached earlier, open the context (right-click) menu, and choose Offline.

10. In the EC2 console, detach the affected volume from the temporary instance and reattach it to your original instance with the device name /dev/sda1. You must specify this device name to designate the volume as a root volume.

11. Start the instance.

12. After the instance passes the health checks in the EC2 console, connect to the instance using Remote Desktop and verify that it boots into DSRM mode.

13. (Optional) Delete or stop the temporary instance you created in this procedure.

To resolve time issues that cause a loss of network connectivity

1. Ensure that you are running the recommended PV drivers. For more information, see Upgrade PV drivers on EC2 Windows instances.

2. Verify that the following registry key exists and is set to 1: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\TimeZoneInformation\RealTimeIsUniversal

1. Open a command prompt, type regedit.exe, and press Enter.

2. In the Registry Editor, choose HKEY_LOCAL_MACHINE from the context menu (right-click), and then choose Find.

3. Type Windows Boot Manager and then choose Find Next.

4. Choose the key named 11000001. This key is a sibling of the key you found in the previous step.

5. In the right pane, choose Element and then choose Modify from the context menu (right-click).

6. Locate the four-byte disk signature at offset 0x38 in the data. This is the Boot Configuration Database signature (BCD). Reverse the bytes to create the disk signature, and write it down. For example, the disk signature represented by the following data is E9EB3AA5:

   ...
   0030  00 00 00 00 01 00 00 00
   0038  A5 3A EB E9 00 00 00 00
   0040  00 00 00 00 00 00 00 00
   ...

7. In a Command Prompt window, run the following command to start Microsoft DiskPart.

   diskpart

8. Run the select disk DiskPart command and specify the disk number for the volume with the disk signature collision.

   Tip

   To check the disk number for the volume with the disk signature collision, use the Disk Management utility. Open a command prompt, type compmgmt.msc and press Enter. In the left-hand navigation panel, double-click Disk Management. In the Disk Management utility, check the disk number for the offline volume with the disk signature collision.

   DISKPART> select disk 1
   Disk 1 is now the selected disk.

9. Run the following DiskPart command to get the disk signature.

   DISKPART>  uniqueid disk
   Disk ID: 0C764FA8

10. If the disk signature shown in the previous step doesn't match the disk signature that you wrote down earlier, use the following DiskPart command to change the disk signature so that it matches:

    DISKPART> uniqueid disk id=E9EB3AA5