osx - Re-Installing Boot2Docker fails due to apparent VirtualBox running - how to shut them down? -

i trying re-install boot2docker from

https://github.com/boot2docker/osx-installer/releases/tag/v1.7.0

the installation fails following error reported:

the installer has detected virtualbox still running. please shutdown running virtualbox machines , exit virtualbox restart installation.

how can exit virtualbox?

open virtualbox, give list of virtualbox vms have. can see of them running, , stop them powering them off.