Once an operating system has been installed the passwords are provided to yourself via email. Over time the password maybe forgotten and you would be looking to rest this password. For ESXi servers, the password reset is different, in the ESXi environment would actually require a reinstallation rather than a password reset.
ESXi 3.5, ESXi 4.x, ESXi 5.x and ESXi 6.0 Reinstalling the ESXi host is the only supported way to reset a password on ESXi. Any other method may lead to a host failure or an unsupported configuration due to the complex nature of the ESXi architecture. ESXi does not have a service console and as such traditional Linux methods of resetting a password, such as single-user mode.