To backup & restore ESXi host configuration proceed with:
Backup via PowerCLI:
Connect-VIServer -Server ESXi_host_IP_address
Get-VMHostFirmware -VMHost ESXi_host_IP_address -BackupConfiguration -DestinationPath C:\
Restore via PowerCLI:
Set-VMHost -VMHost ESXi_host_IP_address -State ‘Maintenance’
Set-VMHostFirmware -VMHost ESXi_host_IP_address -Restore -SourcePath c:\bundleToRestore.tgz -HostUser root -HostPassword exampleRootPassword