- Boot your server from the CD or USB drive containing the ESXi 5.1 installer.
- Press Enter to start the interactive installer.
- When the files are loaded, press Enter to continue.
- Press F11 to accept the EULA.
- Select the disk containing previous installation of ESXi and press Enter.
- When the scanning is completed you will be presented with the following message. Select the Upgrade option and press Enter to continue.
- Press F11 to confirm the upgrade of your ESXi host.
- When the installer finishes the upgrade, remove the installation media from the host and press Enter to reboot.
- When the hosts reboots, you should see the familiar screen with the software version , host name and IP address.
That’s it! You are done. This process takes literally minutes to complete