First, check the VMware HCL to see if the hardware make and model supports ESXi 6.5 or not.

To upgrade from ESXi 5.5 to 6.0 using esxcli:

1. Download the file called update-from-esxi6.5-6.5_update02.zip from My VMware portal.

2. Upload this file to the datastore visible by your ESXi host

datastore.PNG

3. Shut down all VMs running on your ESXi host machine.

4. Connect via SSH and run the following command to enter maintenance mode:

vim-cmd /hostsvc/maintenance_mode_enter

5.  Connect via putty. Note that I’ll use that latest ESXi 6.5 update zip file for this post:

esxcli software sources profile list -d /vmfs/volumes/58048647-ec4971da-a1b8-005056015739/update-from-esxi6.5-6.5_update02.zip

profile list

6. Then update the system using these esxcli commands:

esxcli software profile update -d /vmfs/volumes/58048647-ec4971da-a1b8-005056015739/update-from-esxi6.5-6.5_update02.zip -p ESXi-6.5.0-20180501001s-standard
update

7. Check if any error messages….. then reboot.

8. After reboot verify weather the host has been updated sucessfully or not by running below command:

esxcli system version get

update1

9. After the host has finished booting, exit maintenance mode and power on the virtual machines:

vim-cmd hostsvc/maintenance_mode_exit

Related Information:

You can also install patches using esxcli software profile commands. For more information, see vSphere Command-Line Interface Reference section in the vSphere 5 Command-Line Interface Documentation.