Unable to boot from virtual CD/DVD drive using ISO in VMware virtual machine

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A recently created VM in VMware ESXi (7.0.3) was unable to boot from a mounted ISO. And it turns out this is related to a new virtual EFI boot manager having replaced the previous virtual BIOS.

EFI Boot Manager not booting from mounted ISO

When starting up a VM, you get a tiny moment to press [ESC] to enter the VM's boot menu.

Note: You can increase that moment by modifying the startup delay. This can be done in VM Settings -> VM Options -> Startup Options -> Startup Delay (in milliseconds). Enter 10000 for a 10s delay.

Usually the VM console then shows a small Boot Menu, where you have a couple of options. 

However after this particular (and recently created) virtual machine was started, a [ESC] led to a different kind of boot menu:

A new (EFI) Boot Manager shows up. This seems to be the new default for newly created virtual machines. I assume this happens since ESXi 7.0 but was unable to quickly find a relevant changelog to pin-point the version.

Although the second option (EFI VMware Virtual SATA CDROM Drive) suggests to boot from the virtual CD drive, nothing actually happened when selecting this option and trying to boot the ISO.

Switching to BIOS mode

After shutting down this VM (yes, completely shut down), the boot mode can be changed from EFI back to BIOS. To do so, open the VM Settings -> VM Options -> Startup Options -> Firmware. The default is set to EFI (Recommended) and is greyed out as long as the VM is running:

But as mentioned before, shut down the VM and now you can switch back to BIOS:

Booting mounted ISO with BIOS mode

After another start of the VM and hitting [ESC], the well-known legacy Boot Menu shows up and allows you to select the virtual CD-ROM Drive:

Classic Boot Menu in VMware VM

And this time the mounted ISO was started and the VM successfully booted from the virtual optical drive:

Booting from virtual CD

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Philip from wrote on Apr 20th, 2023:

I am experiencing the same issue.
I can boot from the CD-ROM Drive (which is a Datastore ISO) if I set the Firmware to BIOS.

But I don't what that, I want to use EFI as the Firmware because it also allows Virtualization Based Security and Secure Boot.

Does anyone know how to resolve the issue so that i can boot to my ISO when EFI is set as the Firmware ?