ESXi scripted builds via PXE/kickstart

Periodically we spin up a slew of new hypervisors. If like me you find yourself desiring more automation (and the uniformity that comes with it) but are somewhere between building ESXi by hand and the scale out auto-deploy tooling for hundreds of systems. You may find this useful, especially if you already maintain a kickstart server.

This is my experiences with scripted installations of ESXi 6.5 via kickstart and PXE booting. The beauty of this is it only requires two options set in your DHCP server, the rest of the configuration is static. The net result is, configure your DHCP, let the host PXE boot and within a few minutes you have a repeatable and dependable build process.

So, how to get there?

First up you need to  have the physical environmental basic’s taken care of, e.g. rack & stack, cable up NICs etc. Once that is in place, this process will require DNS entries populated for your new servers, plus explode the ISO on your tftpserver.

n.b. this scripted install uses the “–overwritevmfs” switch so it’s imperative that you do NOT have the host in a state where it can see any storage other than it’s local disks e.g. if you are rebuilding existing hypervisors or the HBA’s have been zoned into something else previously. This is imperative as this switch has the capacity to overwrite the existing filesystems with the new VMFS’d install, therefore it must ONLY see it’s own local disks 😉

Overview of PXE & Kickstart boot workflow:

" <a href=https://www.vmware.com/content/dam/digitalmarketing/vmware/en/pdf/techpaper/vsphere-esxi-vcenter-server-60-pxe-boot-esxi.pdf (pay attention to “/“ and UEFI !)

[1] the boot loader files on the tftpserver. This is an exemplar showing both UEFI and non UEFI sitting side by side on the same install base.

screenshot1

 

[2]  The contents of the CGI script that gleams the FQDN details

screenshot2

[3]  An exemplar of a kickstart file

screenshot3

 

The boot itself

So with that all in place all you need to do is determine if the server you’re booting is legacy BIOS boot or UEFI. The difference being in the boot loader we’ll point at & insert the relevant DHCP-fu for you;

legacy boot

66=your.tftpserver.com

67=esx-6.5/pxelinux.0

UEFI boot

66=your.tftpserver.com

67=esx-6.5/mboot.efi

then simply set the next boot to PXE reboot and watch the little birdy fly!

There you have it. Effectively two DHCP settings and you can rinse and repeat bringing up dozens of systems quickly with repeatable builds. There are of course many other options, all of which have their merits. This one is perhaps most useful if you are already invested in scripted builds/kickstarts.

 

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