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Using ESXi Kickstart %firstboot with Secure Boot

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If you install ESXi via a Kickstart script and make use of the %firstboot option to execute commands on the first boot of the ESXi host after installation, you should be aware of its incompatibility with the Secure Boot feature. If you install ESXi where Secure Boot is enabled, the Kickstart will install ESXi normally only execute up to the %post section. However, it will not execute the %firstboot scripts and if you look at the /var/log/kickstart.log after the host boots, you should see the following message:

INFO UEFI Secure Boot Enabled, skipping execution of /var/lib/vmware/firstboot/001.firstboot_001

If you have Secure Boot enabled, %firstboot is not supported. The reason for this is Secure Boot mandates only known tardisks which can hold executable scripts, and a kickstart script is an unknown source so it can not run when Secure Boot is enabled. If you wish to continue using %firstboot scripts, the only option is to disable Secure Boot and then re-enable it after the installation. A preferred alternative is to convert your %firstboot logic into an external script which can then be applied using the vSphere API (recommended method) and this way you can still customize your ESXi host after the initial installations. I have already filed an internal documentation bug to add a note regarding Secure Boot and %firstboot, hopefully that will roll out with the net documentation refresh.

Quick Tip - What hashing algorithm is supported for ESXi Kickstart password?

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I had a question the other day asking whether the encrypted password which can be specified within an ESXi Kickstart file (denoted by the --isencrypted flag) can use a different hashing algorithm other than MD5? The answer is absolutely yes. In fact, MD5 as a default hashing algorithm has NOT been used for a number of releases, probably dating back to classic ESX (you know, the version that had the Service Console).

For all recent releases of ESXi including 5.5 to 6.7, the default hashing algorithm has been SHA512 for quite some time now. Below are two ways in which you can check which default hashing algorithm is currently being used:

Option 1 - SSH to ESXi host and take a look at /etc/pam.d/passwd


Option 2 - SSH to ESXi host and take a look at /etc/shadow and look at the field prior to the salt.

As a reference:

  • $1$ - MD5
  • $5$ - SHA256
  • $6$ - SHA512

How to Netboot install ESXi onto Apple Mac Hardware?

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The ability to perform an ESXi Scripted Installation over the network has been a basic capability for non-Apple hardware customers since the initial release of classic ESX. However, for customers who run ESXi on Apple Mac Hardware (first introduced in vSphere 5.0), being able to remotely boot and install ESXi over the network has not been possible and customers could only dream of this capability which many of us have probably taken for granted.

Unlike traditional scripted network installations which commonly uses Preboot eXecution Environment (PXE), Apple Mac Hardware actually uses its own developed Boot Service Discover Protocol (BSDP) which ESXi and other OSses do not support. In addition, there are very few DHCP servers that even support BSDP (at least this may have been true 4 years ago when I had initially inquired about this topic). It was expected that if you were going to Netboot (equivalent of PXE/Kickstart in the Apple world) a server that you would be running a Mac OS X system. Even if you had set this up, a Netboot installation was wildly different from a traditional PXE installation and it would be pretty difficult to near impossible to get it working with an ESXi image. With no real viable solution over the years, it was believed that a Netboot installation of ESXi onto Mac Hardware just may not be possible.

tl;dr - If you are interested in the background to the eventual solution, continue reading. If not and you just want the goods, jump down a bit further. Though, I do think it is pretty interesting and worth getting the full context 🙂

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