In the second post of articles about updating ESXi 5.1 to ESXi 5.5, I will cover the interactive upgrade.

Interactive Upgrade

In simple words, interactive upgrade is very similar to the installation of ESXi. Without wasting time let’s upgrade ESXi 5.1 interactively.

1. Insert CD with ESXi image or bootable USB drive into your host.
2. Reboot your host with CD/USB.
3. Select boot from ESXi 5.5 Installer.
   
4. Click Enter to continue.
   
5. Accept End User License Agreement (EULA).
   
6. Installer is searching for previously installed ESXi.
   
7. Select your installed ESXi.
   
8. Choose (X)Upgrade ESXi, preserve VMFS datastore.
   
9. Confirm upgrade by pressing F11.
   
10. Wait for upgrade to finish.
    
11. After successful upgrade (we don’t have any other choice 😉 ) remove installation media and  press Enter to reboot host.
    
12. It worked. ESXi 5.1 was upgraded to latest version which is ESXi 5.5.
    

Series of articles about upgrading ESXi 5.1 to 5.5

https://www.wojcieh.net/upgrade-esxi-5.1-to-5.5-part-1-vmware-update-manager/

https://www.wojcieh.net/upgrade-esxi-5.1-to-5.5-part-2-interactive-upgrade/

https://www.wojcieh.net/upgrade-esxi-5.1-to-5.5-part-3-esxcli/

https://www.wojcieh.net/upgrade-esxi-5.1-to-5.5-part-4-vsphere-auto-deploy/