If you're still using VMware ESXi 4, it's time to upgrade to ESXi 5.
Concerns that the upgrade process will be expensive and complex are unjustified. The software for the VMware ESXi 5 hypervisor is available for free on the company’s website, and the download procedure is pretty straightforward. This article will walk you through the process.
Preparing for your ESXi 5 upgrade
Before starting your VMware ESXi upgrade, you need to download the ISO file from the VMware website. On the download page, you'll also find a license key. Make sure to write it down, because you can only use an unlicensed version of VMware ESXi 5 for 60 days.
After burning the ISO to a CD, shut down the existing ESXi host and reboot it from the optical drive. This will load the installation program and, after accepting the license agreement, you can select the disk where the existing VMware ESXi is installed. The installation program will show you the devices it finds that contain a Virtual Machine File System (VMFS). Select this disk to start performing your upgrade to VMware ESXi 5.
VMware ESXi upgrade options
You'll now see three options for upgrading to VMware ESXi 5. The first option -- the most common one -- is to upgrade VMware ESXi while keeping all your ESXi settings and the current VMFS data store, including all its VMs. The second option re-installs ESXi, meaning you’ll lose your ESXi settings but still keep the VMFS data store. Only use this option if you have problems with your virtual machines (VMs) and you want to re-import the VMs while keeping only their disk files. It gives you a clean install, and you will have to re-add the VMs back to your inventory after the upgrade. This approach to a VMware ESXi upgrade is not the best choice, but it may help if a normal upgrade fails.
The third option allows you to wipe everything that’s currently installed and start a completely new VMware ESXi installation, but most customers won’t need to do that.
For a normal ESXi upgrade of a host that works fine, you should select the option to upgrade while keeping the VMFS data store. The installation program will then gather system information (this may take a while). Next, you'll see a message stating that the installer is ready to start the VMware ESXi 5 upgrade.
In this message, you'll see the current version of VMware ESXi and the version the installer will upgrade to, as well as the name of the disk that contains the current installation. Double check this information, as VMware does not support a rollback. To proceed, press the F11 key. Once the ESXi upgrade has been completed, you need to reboot the host to start VMware ESXi 5.
Upgrading the vSphere Client
After upgrading your hosts to VMware ESXi 5, you also have to upgrade the vSphere Client. As there is no information stored in the vSphere Client itself, you can just download the installation file and run the installer on a Windows workstation. The Client installer will self-extract, and the installation will start automatically. Just complete the wizard to finalize the installation.
After the upgrade is finished, log in through the vSphere Client, and on the host, select the Configuration tab and go to Licensed Features. You'll notice that it still shows an evaluation license that expires in 60 days. To change this, click Edit and select “assign a new license key to this host.” Next, click Enter Key, and enter the license key that you registered when downloading the ISO file from the VMware website.
Now, your upgraded VMware ESXi host is ready to go. If you chose the simplest upgrade option, all the information in the VMFS data store is still there, so there’s no need to make any modifications. Power on your VMs and get started using VMware ESXi 5.
This was first published in December 2011