Quick Tip - Automating ESXi 8.0 install using allowLegacyCPU=true

For those looking to install ESXi 8.0 but have an unsupported CPU, the following kernel boot option allowLegacyCPU=true can be added which would bypass the installer pre-check as shown in the screenshot below.

When the ESXi installer bypass happens, instead of an error which forces you to reboot, you will get a warning message and user must acknowledge they understand they are using an unsupported CPU and then continue with the installation.

UPDATE (10/05/23) - ESXi 8.0 Update 2 requires CPU processors that support XSAVE instruction or you will not be able to upgrade and means you will hardware with a minimum of an Intel Sandy Bridge or AMD Bulldozer processor or later.

Note: For more information, also checkout my vSphere 8 Homelab considerations blog post for more tips and tricks.

For an interactive installation of ESXi, the additional acknowledgment is not an issue but for an automated installation of ESXi using Kickstart, this can be a problem since you are still required to manually hit enter before the installation actually begins. The question from a couple of my readers, is there a workaround for this?

Yes and there are actually a couple of options that can be passed into ESXi Kickstart script depending on which pre-check messages you would like ignored for automated installations.

• --ignoreprereqwarnings - Will ignore warning messages
• --ignoreprereqerrors - Will ignore error messages
• --forceunsupportedinstall - Will ignore error/warning messages for deprecated CPUs

As you can see from the screenshot above (testing ESXi 8.0 on 2011 Apple Mac Mini), I have both an error for my unsupported CPU and a warning for my unsupported network adapter and so BOTH ignore warning/error options will required for the ESXi installer to continue with the installation without prompting for user input.

Here is a working Kickstart example that demonstrates the use of the two options:

vmaccepteula
install --firstdisk=local --overwritevmfs --ignoreprereqwarnings --ignoreprereqerrors
reboot

network --bootproto=static --ip=192.168.30.13 --netmask=255.255.255.0 --gateway=192.168.30.1 --hostname=nuc.primp-industries.com --nameserver=192.168.30.1 --addvmportgroup=1
rootpw VMware1!

%firstboot --interpreter=busybox

# enable & start SSH
vim-cmd hostsvc/enable_ssh
vim-cmd hostsvc/start_ssh

# enable & start ESXi Shell
vim-cmd hostsvc/enable_esx_shell
vim-cmd hostsvc/start_esx_shell

# Suppress ESXi Shell warning
esxcli system settings advanced set -o /UserVars/SuppressShellWarning -i 1

Note: In some cases, you may need all three options to successfully install ESXi without any prompts due to deprecated CPUs rather than unsupported CPUs