VMware ESXi host Upgrade 5.5 to 6.5 – Method 1 – Interactive ESXi upgrade

Alternative Method
How to configure VMware Update Manger & Upgrade ESXi Host in vCenter Appliance 6.7 – Full Demo
https://www.youtube.com/watch?v=TODFu5f5WsY

You can run the ESXi 6.0 installer from a CD/DVD or USB flash drive to do an interactive upgrade or migration. This method is appropriate for deployments with a small number of hosts. The installer works the same way for a fresh installation, but if you select a target disk that already contains an ESXi 5.x installation, the installer upgrades the host to ESXi 6.0 and gives you the option to migrate some existing host settings and configuration files and preserve the existing VMFS datastore.