You can start and stop each one of the major vSphere components, ESXi, and vCenter Server. You might want to stop a component to perform maintenance or upgrade operations. Start an ESXi HostWhen you install ESXi, it starts itself through the installation reboot process. If your ESXi host is shut down, you must manually restart it. Reboot or Shut Down an ESXi Host in the vSphere Web ClientYou can power off or restart any ESXi host by using the vSphere Web Client. Powering off a managed host disconnects it from vCenter Server, but does not remove it from the inventory. Starting vCenter ServervCenter Server runs as a Windows service. vCenter Server starts when you start the Windows machine on which it is installed. It also restarts when that machine is rebooted.