Custom ESXi ISOs with a Kickstart Template
Explore custom ESXi ISOs with a Kickstart template for repeatable host builds. Review install-disk selection notes and linked setup resources.
Overview
I use custom ESXi ISOs with Kickstart files to make rebuilding my physical homelab hosts more repeatable. This post shares the template and build resources I used, along with install-disk selection notes; it is not a complete ISO-building walkthrough.
Template inputs and installation safety
Before adapting the downloadable Kickstart template, record and review these environment-specific inputs. The linked Word document is a starting point, not a validated installer for every ESXi release.
| Input | Check |
|---|---|
| Target disk | Match the stable disk identifier to the physical device intended for installation. Review every install/clearpart/overwrite option before booting unattended. |
| Identity and network | Unique FQDN, static address, mask, gateway, DNS, management VLAN and the correct uplink device. |
| Host setup | NTP, release-matched ESXi image and any first-boot commands appropriate to that build. |
| Credentials | Use the release-supported password mechanism; do not publish live passwords or password hashes in the template, ISO or repository. |
- An unattended installer can overwrite the wrong disk without a useful recovery point. Back up required data and test the template on a disposable VM or isolated spare host first.
- Verify the target device on every host rather than assuming identical controller enumeration. Disconnect unrelated storage where the approved installation procedure allows it.
- Keep generated ISOs and Kickstart files access-controlled, and remove staging copies when no longer needed. Rotate any credential accidentally exposed in a shared artifact.
Plan the Kickstart installation
VMware allows the utilization of a kickstart file to be injected in the ISO so that you can make it an almost silent install. The hardest part for me to build custom ISOs was being able to locate the install disk that I wanted to put vsphere on. There are many was to obtain this disk name but I ended up using a generic vsphere iso and loading that on each host in order to get the name for all the disks that I am going to use. While not the most efficient way of obtain those names it was the easiest in the end for me, just took some time to load each host up with the iso.
Build resources
I don’t believe in re-inventing the wheel so I am not going to provide the step by step instructions on how to build a custom ISO, there are plenty of other good write-ups out there and a couple of the ones I use are below:
https://williamlam.com/2019/07/automated-esxi-installation-to-usb-using-kickstart.html
https://vcloud-lab.com/entries/blog/vmware-esxi-unattended-setup-building-a-kickstart-enabled-custom-iso-from-scratch
Download the Kickstart template
I used both of those above resources to build my custom ISOs for my physical hosts and I also found multiple examples for kickstart file configurations which ultimately let me to settle on something similar to the example below:
Feel free to use this to start your own kickstart installs, these are great at helping you get your ESXi hosts prepared for VMware Cloud Foundation (VCF) deployments and just overall maintaining consistency in your hosts.