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Quick Tip - Auditing ESXi boot firmware type

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I had a customer that recently reached out asking how they could easily audit their entire ESXi infrastructure to determine which hosts was still booting using the legacy BIOS firmware, which has been deprecated and will be removed in a future vSphere release, in favor of the industry standard UEFI firmware type.

In vSphere 8.0 Update 2, a new vSphere API property called firmwareType was introduced and added to the ESXi Hardware BIOS info object that makes it very simple to retrieve with the following PowerCLI 1-Liner:

(Get-VMHost).ExtensionData.Hardware.BiosInfo

Here is an example output for an ESXi host booting with UEFI firmware:


Here is an example output for an ESXi host booting with BIOS firmware:


Since this vSphere API property was recently introduced in vSphere 8.0 Update 2, if you attempt to use this on an ESXi host that is not running 8.0 Update 2, then you will see the field being blank if you are using a newer release of PowerCLI that understands this new property or it will simply not show if you are using an older version of PowerCLI.


Alternatively, if you still need to retrieve this information, you can go directly to ESXi host via SSH, not ideal but you can use the following VSISH command to retrieve this exact information:

vsish -e get /hardware/firmwareType

Easier method to simulate custom ESXi SMBIOS hardware strings

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Happy 2025! ? Here is a fun one to kick off the New Year ☺️

Last year, I demonstrated a method for customizing the SMBIOS hardware string using Nested ESXi, but the solution was not perfect and required hacking up a VM ROM file and it was also limited to using the BIOS firmware for your Nested ESXi VM as the behavior for EFI firmware was different.

I was doing some research towards the end of last year and I came across a much more elegant solution that works for both physical and virtual ESXi!

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Sharing a single NVMe device with NVMe Tiering, ESXi-OSDATA & VMFS Datastore? 

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With the ability to to share a single NVMe device for both NVMe Tiering and a local VMFS datastore ... I had an idea to push this further and see if I could also get an ESXi-OSData partition running on the same shared NVMe device! ?

Simliar to the previous blog post, the underlying use case is really for dev/test environment where you may not have a ton of NVMe devices to dedicate to the various ESXi functions, especially true for those using small form factor (SFF) systems like an ASUS NUC or simliar. Most of the mainstream SFF systems usually comes with two, maybe three NVMe slots if you are lucky.

This technique would allow you to boot ESXi off of USB and then have key functions like ESXi-OSData and NVMe Tiering on a single shared NVMe while freeing up the other NVMe devices for use with vSAN, which you should have dedicated devices for whether you are considering vSAN OSA or ESA.

Disclaimer: This is not officially supported by VMware, please use at your own risk.

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