Issue: Debian 11 VM restored from VMware to Nutanix AHV fails to boot – Boot device not found and GRUB cannot find LVM root volume

1. Issue description

We are experiencing a boot failure after restoring a Debian Linux virtual machine from VMware vSphere to Nutanix AHV using Veeam Backup & Replication / Veeam Agent backup.

The restored VM does not boot and displays the following AHV boot error:

Unable to find a valid boot device.
VM currently configured as BIOS.

During other restore attempts, the VM also displayed the following grub error

error: disk 'lvmid/...' not found.
Entering rescue mode...
grub rescue>

The issue persists despite several restore attempts and changes to the disk bus configuration.

We would like Veeam to investigate whether this behaviour is related to the restore process, particularly the reconstruction of the virtual disks and LVM metadata when restoring a Linux Agent backup to Nutanix AHV.

2. Source environment

• Operating system: Debian GNU/Linux 11.11

• Hypervisor: VMware vSphere

• Firmware: BIOS (legacy BIOS, not UEFI)

• Original virtual disk controller/bus: SCSI

• Disk layout: Linux LVM

• Backup method: Veeam Agent backup

Other Veeam Agent backups of physical Windows machines have previously been restored successfully in the same environment.

Initramfs contain VirtIO Drivers.

3. Target environment

• Hypervisor: Nutanix AHV

• Firmware: BIOS

• Virtual disks configured with SCSI bus during the latest restore attempts.

• Restore performed using the Veeam restore plugin for Nutanix AHV.

The original VM appears to have one virtual disk in vSphere, whereas the restored VM has been observed with two virtual disks in AHV. This is expected as per documentation Restoring Veeam Agent Backup to Nutanix VM

4. Restore attempts and actions already performed

Several restore attempts and configuration changes have been performed:

1. Initial restore:

   • The restored VM was presented with SATA disk(s), although the original disk was configured as SCSI.

   • The VM failed to boot.

2. Manual disk configuration:

   • The disk bus configuration was modified.

   • The VM eventually reached GRUB, but GRUB failed to locate the LVM root volume.

   • Error observed: error: disk 'lvmid/...' not found.

3. Disk removal:

   • The additional SATA disk was removed from the cloned VM.

   • The same GRUB error remained.

4. Restore plugin configuration:

   • The plugin configuration initially showed:

     • BusesFillingOrder: "SATA, SCSI, IDE, PCI"

     • IgnoreOriginalBus: false

   • The bus filling order was modified to prioritize SCSI.

   • A new restore was performed.

   • The restored disks were then presented as SCSI disks, but the VM still failed to boot.

   • AHV displayed the error: Unable to find a valid boot device.

5. BIOS/UEFI verification:

   • The source VM uses BIOS.

   • The restored AHV VM is also configured for BIOS.

   • A BIOS/UEFI mismatch is therefore not currently suspected.