Overview of the Upgrade process for ESXi host 6.5

You can upgrade a ESXi 5.5.x host or 6.0.x host, asynchronously released driver or other third-party customizations, interactive upgrade from CD or DVD, scripted upgrade, or upgrade with vSphere Update Manager. When you upgrade an ESXi 5.5.x host or 6.0.x host that has custom VIBs to version 6.5, the custom VIBs are migrated.High level steps for upgrading ESXi:

• Verify that your system meets the upgrade requirements. See ESXi Requirements.
• Prepare your environment before upgrading. See Before Upgrading ESXi Hosts.
• Determine where you want to locate and boot the ESXi installer. See Media Options for Booting the ESXi Installer. If you are PXE-booting the installer, verify that your network PXE infrastructure is properly set up. See PXE Booting the ESXi Installer.
• Upgrade ESXi. See Upgrading ESXi Hosts.
• After upgrading ESXi hosts, you must reconnect the hosts to the vCenter Server and reapply the licenses. See After You Upgrade ESXi Hosts.

Image: VMware

• Use the interactive graphical user interface (GUI) installer from CD, DVD, or USB drive.
• Scripted upgrade.
• Use the esxcli command line interface (CLI).
• vSphere Auto Deploy. If the ESXi 5.5.x host was deployed by using vSphere Auto Deploy, you can use vSphere Auto Deploy to reprovision the host with a 6.5 image.
• vSphere Update Manager.