Purpose:
The purpose of this document is to review the differences between Legacy BIOS PXE booting, UEFI PXE booting and why it matters.
What is the difference:
The difference is the process that the firmware uses to find the boot target, Legacy Boot is the boot process used by BIOS firmware and UEFI boot is used by UEFI firmware. UEFI is the newer standard and is more secure. In regards to imaging the major difference is the partition structure used. UEFI booted systems use a GPT (GUID Partition Table) partition structure where Legacy BIOS booted systems use a MBR (Master Boot Record) partition structure.
Why it matters:
The default option when creating a provisioning template is to use LANDESK ImageW v2, this method captures/deploys the entire partition including the partition table structure. The other most common method to capture/deploy is using ImageX, ImageX captures just the bytes on the drive and does not contain the partition table structure. If you are using ImageX with a .wim extension this information is not applicable since ImageX does not capture the partition table structure.
When is this important:
This information is important if you have an environment with both Legacy BIOS booting machines as well as UEFI booting machines and you are using an ImageW (.tbi) image. This is because an image captured with ImageW has the partition structure so you can not capture on a Legacy BIOS booting machine then deploy to a UEFI booting machine because the partition structure is not compatible. They are starting to make systems without the Legacy BIOS boot option so that is also something to keep in mind.
More information:
What happens if I deploy a .tbi file that was captured with a Legacy BIOS booting device and attempt to deploy to a UEFI booting machine or vice a versa? The image will deploy successfully, however on first boot the firmware will be unable to find the boot device and will act as if there is no OS installed.
Useful links:
- Boot to UEFI Mode or Legacy BIOS mode | Microsoft Docs