Please advise me how to reset the root password of ESXi host
Suggest me the best practice.
If its ESXi there are no safer ways other than re-installing it.
You can have look at this KB: VMware KB: Changing a forgotten root password on an ESX/ESXi host
like dGeorgey said re installation of the esxi hypervisor is the best method.
I havent tested the following but if you NEED the password
try this
http://www.vdsyn.com/resetting-the-root-password-for-esxi-5-x/
If you have option to use host profiles you could use host profiles. Please refer to link.
http://blog.shiplett.org/lost-your-esxi-root-password-reset-it-with-host-profiles/
Keder_D's solution could only work if op has Vcenter, and not a stand alone esxi host,
and just to be clear, you can in fact 'reset' the password if you know the current password. The re-install is only required if you don't know the current password.
sparrowangelstechnology, one of my coworkers once used the live CD on a UNIX system (not ESXi) technique and worked perfectly.
I think there is a really good chance this would work with a vSphere host, I think I'll test it out when I get a chance.