There was an interesting discussion on our internal Socialcast platform last week on figuring out how an ESXi host is booted up whether it is from local device like a disk or USB device, Auto Deploy or even boot from SAN along with its respective boot device? Although I had answered the question, I was not confident that we actually had a reliable and programmatic method for identifying all the different ESXi boot methods, which of course piqued my interest.

With a bit of trial and error in the lab, I believe I have found a method in which we can identify the ESXi boot type (Local, Stateless, Stateless Caching, Stateful or Boot from SAN) along with some additional details pertaining to the boot device. To demonstrate this, I have created the following PowerCLI script ESXiBootDevice.ps1 which contains a function called Get-ESXiBootDevice.

The function can be called without any parameters, in which it will query all ESXi hosts for a given vCenter Server and/or standalone ESXi host. You can also specify a specific ESXi host by simply passing in the -VMHostname option.

Here is an example output for one of my lab environments which shows several ESXi hosts and their different boot methods from local disk to Auto Deploy which can include stateless, stateless caching and stateful deployments. Depending on the BootType, the boot device shown in the Device column will either be the MAC Address of the NIC used to network boot the ESXi host or the identifier of a disk device. I have also included some additional details such as vendor/model along with the media type (SAS, SSD or USB) which is available as part of ESXCLI.

This script also supports ESXi environments that boot from SAN (FC, FCoE or iSCSI) and you can easily identify that with the word "remote" for the BootType. I would like to give a huge thanks to David Stamen who helped me out with the boot from SAN testing.