Restore to AWS EC2 Fails with: "ClientError: Unknown OS / Missing OS files" or "FirstBootFailure"
| KB ID: | 4814 |
| Product: | Veeam Backup & Replication | 12.3 | 12.3.1 | 12.3.2 | 13 |
| Published: | 2026-01-21 |
| Last Modified: | 2026-10-27 |
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This article applies to Veeam Backup & Replication versions prior to 13.1.0.411 (12.3.2.x / 13.0.x).
Starting with Veeam Backup & Replication build 13.1.0.411, this issue no longer occurs.
The workarounds described in this article are not required in 13.1.0.411 and later.
Challenge
When restoring a VM to AWS EC2, one of the following errors occurs:
StatusMessage: "CLIENT_ERROR : ClientError: Unknown OS / Missing OS files."
Failed to import machine to Amazon EC2: CLIENT_ERROR : FirstBootFailure: This import request failed because the instance failed to boot and establish network connectivity.
Cause
Solution
Direct recovery to AWS EC2 without using the helper appliance works successfully and does not encounter this issue.
Note: This issue does not affect the restore of AWS EC2-native VMs. For those EC2-native VMs, it is recommended to use the helper appliance.
For Veeam Backup & Replication 13.0.x
In Veeam Backup & Replication 13.0.x (e.g., 13.0 and 13.0.1), disable the option "Use the helper appliance" in the restore wizard.
Reference: Restoring to Amazon EC2 > Step 8. Configure Helper Appliance
Note: A solution to resolve the root issue was included starting in Veeam Backup & Replication 13.1.0.411.
For Veeam Backup & Replication 12.3.x
In Veeam Backup & Replication v12.3.x (e.g., 12.3, 12.3.1, and 12.3.2), the option for "Use the helper appliance" during the restore process is greyed out and cannot be disabled. To make the option selectable, create the following registry value on the Veeam Backup Server. After configuring the registry value, the “Use helper appliance” option should be disabled when restoring non-AWS EC2-native VMs to AWS EC2.
Key Location: HKLM\SOFTWARE\Veeam\Veeam Backup and Replication\
Value Name: PublicCloudRestoreEnableApplianceSelection
Value Type: DWORD (32-Bit) Value
Value Data: 1
Note: The Veeam Backup & Replication Console must be closed and reopened for the setting to take effect.
PowerShell command to set registry value:
If the Helper Appliance Cannot Be Avoided
Restoring without the helper appliance, as described above, is the recommended approach. When restoring without the helper appliance is not possible, the AmazonZeroDisksOnRestore registry value can be created to enable a disk pre-zeroing mechanism that allows the restore to complete successfully while the helper appliance is used.
Note: The pre-zeroing mechanism significantly increases restore time. The restore can be two to three times slower than a regular data upload.
This registry value is available in all Veeam Backup & Replication 12.3.2.x and 13.0.x builds, and was removed starting in 13.1.0.411.
Key Location: HKLM\SOFTWARE\Veeam\Veeam Backup and Replication\
Value Name: AmazonZeroDisksOnRestore
Value Type: DWORD (32-Bit) Value
Value Data: 1
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