One of the changes with the release of ESXi 4.1 was the removal of the vSphere Host Update Utility (HUU) from the vSphere client installation. This tool was especially useful for patching stand-alone hosts. Hosts managed with any version of vCenter can be patched with Update Manager, but for stand-alone hosts the alteratives are the vCLI and PowerCLI.
However, you can still use the HUU from the vSphere 4.0 client installation to patch your ESXi hosts. If you don’t have version 4.0 of the client installed, download the client following these instructions. If neither of those methods works for you, you can access the patches download site for ESXi 4.0, download 4.0 Update 2, and then extract the vSphere client installation using a process similar to this. If you have version 4.1 or later of the vSphere client installed, you don’t have to remove those clients prior to the 4.0 client installation. Ensure that you check the option to install the HUU. For early versions of the 4.0 client select a Custom installation to choose the HUU option.
Once you have the 4.0 client installed, go to the VMware program group and start the HUU. Click Add Host and enter the IP address or hostname for your ESXi 4.1 host. Click Scan For Patches and enter appropriate credentials for your host.
Once the patches have been identified for the host, click Patch Host. Note that this operation puts the host into maintenance mode and no VMs can run on the host while it is in maintenance mode.
Once the patch process has completed, the host is rebooted. The patching process can take some time as the HUU has to download the update patch files.
After the host has rebooted, check that the host is up to date.
Sample log file for the patching process. In this case the host was updated from the GA release of 4.1 to 4.1 Update 1.
Patching 192.168.50.134 Start uploading files to host Metadata and binaries have been successfully uploaded Scanning the host completed Start installing patches Installing patches on 192.168.50.134 : ESXi410-201101201-SG, ESXi410-201101202-UG, ESXi410-201101223-UG, ESXi410-201101224-UG, ESXi410-Update01 Trying to put the host into maintenance mode Entered maintenance mode successfully Start uploading files to host Metadata and binaries have been successfully uploaded Start rebooting host 192.168.50.134 Start rebooting host Host reboot started successfully, Please make sure the host is successfully booted Reboot host succeeded 192.168.50.134 Installing patches succeeded on host 192.168.50.134 Installation of patches succeeded Patching has succeeded. The host will be rebooted....Success