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How to prompt for user input during an interactive or scripted install of ESXi?

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A question that continues to pop up from time to time is whether it is possible to prompt for user input during an interactive or scripted installation of ESXi? This is actually something I have written about before using PXE boot options as a workaround to provide for a semi-interactive automated installation of ESXi. The most recent request for this was not actually from a customer but rather someone internally working at VMware. The individual noted that he had already read my blog and a few other references but was still hopeful for a solution. I remember when I had looked into this problem several years back, I was not able to find anything and the inquiries to VMware (which I was still a customer at the time) came up empty.

UPDATE (01/10/19) - For ESXi 6.5 or greater, please take a look at this blog post for an updated solution

After replying back to the individual with the information that I had, it actually got me thinking which is usually not good 😉 Having just recently finished building a new Kickstart environment to test UEFI PXE boot for ESXi 6.0, I figure I might as well take another look at this topic again. I wanted to see if there was something that could be done with one of the /dev/ttyl (teletype) interfaces while the ESXi Installation was running. I did a couple of Google searches and to my surprise, there was someone on the VMTN Community forum who had already solved this problem and posted a solution almost 1 year before my article, not sure how I could have missed that?!

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How to create custom ESXi boot menu to support multiple Kickstart files?

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I recently received a question from one of my readers who was looking to migrate from ESXi 4.1 to newer version and one of the challenges they faced was around their ESXi scripted installs, better known as ESXi Kickstart. Previously, they had relied on using a custom syslinux boot menu to be able to select a specific Kickstart configuration file that resided locally on a bootable ESXi Image (USB, ISO or CDROM) as a PXE/DHCP environment was not allowed in their environment. There was a small change to how ESXi boot files were reference between ESXi 4.x and ESXi 5.x/6.x and a new boot.cfg configuration is now used which I had written about here with respect to scripted installs when ESXi 5.0 was first released.

UPDATE (07/25/25) - See this blog post HERE to create custom UEFI custom boot menu

Luckily, even with these changes one can still use a custom menu with ESXi 5.x/6.x and be able to select a specific Kickstart configurations based on user input. Here is a screenshot example of a custom ESXi Image that I built providing three different install options that could be selected which would map to three different Kickstart configurations which can be either local to the boot media or can also be retrieved remotely.

bootable-esxi-image-with-multiple-kickstart-option
The first thing you should be aware of if you plan to boot the custom ESXi Image from local media such as USB, CDROM or ISO is that the path to the Kickstart file must be in all UPPER CASE which is mentioned in this VMware KB 1026373. The next caveat that I found in my testing is that if you plan to store the local Kickstart files inside of a directory within the ESXi Image, the name of the directory can not be too long. I would recommend using "ks" as "kickstart" apparently was too long.

After you have extracted the contents of an ESXi ISO which you have downloaded, you will want to create a root directory called "ks" which will contain the different Kickstart configuration files. Here is an example of what structure look like:

ks
├── ks1.cfg
├── ks2.cfg
└── ks3.cfg

Next, you will need to edit the isolinux.cfg file which comes by default within the ESXi ISO. This is where you will add the different Kickstart options that a user will be able to select from. In this first example, we will look at referencing the Kickstart files locally on the media which can be either USB or CDROM and you will need to ensure you specify the right boot option as shown here in the VMware documentation. The path to the Kickstart file needs to be appended to the line that contains boot.cfg reference and you must ensure you include "+++" at the end of that line.

Here is an example of referencing a Kickstart file that lives on a USB device under this path /ks/ks.cfg:

APPEND -c boot.cfg ks=usb:/KS/KS.CFG +++

Here is an example of my isolinux.cfg for the boot menu that I have shown above which provides three different options mapping to three different Kickstart configuration files:

DEFAULT menu.c32
MENU TITLE vGhetto Custom ESXi 6.0 Boot Menu
NOHALT 1
PROMPT 0
TIMEOUT 80
LABEL Ghetto Install
  KERNEL mboot.c32
  APPEND -c boot.cfg ks=cdrom:/KS/KS1.CFG +++
  MENU LABEL ^1 Ghetto Install
LABEL A bit More Ghetto Install
  KERNEL mboot.c32
  APPEND -c boot.cfg ks=cdrom:/KS/KS2.CFG +++
  MENU LABEL ^2 A bit More Ghetto Install
LABEL Super Ghetto ESXi Install
  KERNEL mboot.c32
  APPEND -c boot.cfg ks=cdrom:/KS/KS3.CFG +++
  MENU LABEL ^3 Super Ghetto ESXi Install
LABEL hddboot
  LOCALBOOT 0x80
  MENU LABEL ^Boot from local disk

As I mentioned earlier, the Kickstart configuration file can either be retrieved locally or it can also be retireved remotely using one of the following supported protocols: http, https, ftp & nfs as shown here in the VMware documentation.

Here is an example of isolinux.cfg for a boot menu which references both a local kickstart as well as one that remotely lives on a web server:

DEFAULT menu.c32
MENU TITLE vGhetto Custom ESXi 6.0 Boot Menu
NOHALT 1
PROMPT 0
TIMEOUT 80
LABEL Ghetto Install
  KERNEL mboot.c32
  APPEND -c boot.cfg ks=cdrom:/KS/KS1.CFG +++
  MENU LABEL ^1 Ghetto Install
LABEL A bit More Ghetto Install
  KERNEL mboot.c32
  APPEND -c boot.cfg ks=http://172.30.0.108/ks/ks2.cfg +++
  MENU LABEL ^2 A bit More Ghetto Install
LABEL Super Ghetto ESXi Install
  KERNEL mboot.c32
  APPEND -c boot.cfg ks=http://172.30.0.108/ks/ks3.cfg +++
  MENU LABEL ^3 Super Ghetto ESXi Install
LABEL hddboot
  LOCALBOOT 0x80
  MENU LABEL ^Boot from local disk

For additional ESXi Kickstart resources and example, be sure to check out my pages here.

How to automate VM deployment from large USB keys using ESXi Kickstart?

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During VMworld US, I had the opportunity to speak with several customers to learn about their VMware environment and some of the challenges they were facing. In some scenarios, I was able to offer a solution or a different way of solving the problem. For others, it was primarily feedback on how we can better improve some of our capabilities/features or specific feature requests they would like to see get added.

One interesting challenge that arose from a class of customers who manages hundreds of remote sites is the ability fully automate the provisioning of an ESXi host as well as set of Virtual Machines as part of the initial deployment. The provisioning is all done through Kickstart (unattended installation of ESXi) and usually from a USB device but it could also be from a custom ISO. One ask that kept coming up was the support for larger USB key support within ESXi so that it could be used to include additional payload.

As some of you may or may not know, ESXi can only access USB devices within the ESXi Shell formatted using the FAT16 filesystem which allows for a maximum file size of 2GB for each partition. However, this limitation is only for the ESXi Shell itself and for the size of the ESXi installation media, this is more than sufficient. If you wish to leverage larger USB keys which has increased significantly in recent years from 32GB, 64GB and even 128GB, you can directly pass that into any guest OS through the USB Arbitrator Service (enabled by default) and there you will be able to consume the entire capacity of the USB device. The challenge is how do you go about bootstrapping ESXi as well as the initial set of Virtual Machines with these limitations and completely automated using an ESXi Kickstart?

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