Wondering how to boot an EC2 Windows instance into DSRM? Take a peek at this blog.

Sometimes, if an instance running on the Microsoft Directory experiences a system failure or other critical issues then we can troubleshoot the instance by booting it into a Safe Mode called Directory Services Restore Mode(DSRM).

Here at Bobcares, we have seen several such AWS-related queries as part of our AWS Support Services for AWS users, and online service providers.

Today we’ll take a look at how to boot an EC2 Windows instance.

Boot an EC2 Windows instance into DSRM(Directory Services Restore Mode)

Now let’s see how our Support Engineers boot an EC2 Windows instance.

Enabling the DSRM and booting into the instance depends on the driver the instance is running. Driver versions like ‘AWS PV 7.2.2 and later’ and ‘Enhanced Networking’ support DSRM.

If the driver version is ‘AWS PV 7.2.2 and later’ and ‘Enhanced Networking’, to enable the DSRM, we need to first, detach the root volume. Then attach it to another instance and then enable the DSRM.

Configure an instance to boot into DSRM

Since the EC2 Windows instances do not have network connectivity before the operating system is running, we can’t press F8 button for booting. We can do it by following one of the below procedures.

Booting an online instance into DSRM using the System Configuration dialog box

• First, we type MSConfig in the Run dialog box and press Enter.
• Next, we choose the Boot tab.
• After that, under Boot options, we choose Safe boot.
• Then we choose Active Directory repair and then choose OK. The system prompts us to reboot the server.

Booting an online instance into DSRM using the command line

From the Command Prompt window, we run the following command:

bcdedit /set safeboot dsrepair

If an instance is offline and unreachable, we can detach the root volume and attach it to another instance to enable DSRM mode.

Booting an offline instance into DSRM

• First, we open the Amazon EC2 console at https://console.aws.amazon.com/ec2/.
• Next, in the navigation pane, we choose Instances.
• Then, we locate and select the affected instance and choose Instance state, Stop instance.
• After that, we choose Launch instances and create a temporary instance in the same Availability Zone as the affected instance. Then we choose an instance type that uses a different version of Windows.
• In the navigation pane, we choose Volumes.
• We then locate the root volume of the affected instance. Then we detach the volume and attach it to the temporary instance we created earlier. After that, we attach it with the default device name.
• We use Remote Desktop to connect to the temporary instance, and then use the Disk Management utility to make the volume available for use.
• Then we open a command prompt and run the below command. Note: Replace D with the actual drive letter of the secondary volume just attached:

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

• In the Disk Management Utility, we choose the drive we attached earlier. Then we open the context (right-click) menu, and choose Offline.
• 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.
• After that, we start the instance.
• Once the instance passes the health checks in the EC2 console, we connect to the instance using Remote Desktop and verify that it boots into DSRM mode.

[Need any further assistance in booting the EC2 Windows instance? – We are here to help you.]

Conclusion

Today, we saw how our Support Engineers boot an EC2 Windows instance into DSRM