Updating VMware ESX(i) 3.5 Update5/4.0 to ESX(i) 4.1 with esxupdate command

Note:-
*Make sure there are no virtual machines present in the host (move the VMs/virtual_machines using vmotion)
*Using the vpshere client put the host in maintenance mode(right click on the host>enter maintenance mode).
1. Download the .zip and the .zip.
2. create an ssh connection to the host which you want to upgrade. example:- putty software.
3. run the following command
mkdir /tmp/upgrade
4. copy the download upgrade bundles to the upgrade directory. example:-WinSCP software
5. go back to the ssh connection command line (putty software) and run the command
cd /tmp/upgrade
or you can also upload the file to any datastore in a temporary folder.
esxupdate --bundle=<offline-bundle>.zip update
or
esxupdate --bundle <offline-bundle>.zip update
6. wait for the installation.
7. It will ask you for a reboot
8. run the following command
shutdown -r now
9. Go back to the vSphere client and reconnect to the host, exit out of the maintenance mode.
Note:-
* If you still see the old version of the host (4.0 instead of 4.1) then exit out of the vcenter server>click on start>run>services.msc>restart vcenter services and relog into the vcenter server using the vsphere client.