I am using Virtual box to import sandbox image 2.5, I use power off.
I just want to know is this the right way to do it.
I haven't exhaustively tested this with the new 2.5 Sandbox, but I've been using the following command pretty successfully from the CLI to shutdown things completely and everything comes back up nice on a restart.
shutdown -P now
Since you are running java services it's recommended you shut them down before powering off the sandbox. You can do this easily with the "Stop all" underneath "Services" button in the ambari dashboard. Then you can safely use Power Off from the vmware/virtualbox UI.