Ubuntu server 16.04.3 with Kubuntu installed, using Virtualbox Version 5.1.28 r117968 (Qt5.5.1) from official repo, host UEFI on with signed kernel modules, Windows 7 Ultimate x64 guest.
When I start the guest in headless mode the option to detach with guest still running is missing when I click the X close button on the guest's Virtualbox window. However the main Virtualbox window shows a 'Show' button as if it's window could be closed...
Screenshot:
https://imgur.com/a/x55gW
When I start the guest in headless mode the option to detach with guest still running is missing when I click the X close button on the guest's Virtualbox window. However the main Virtualbox window shows a 'Show' button as if it's window could be closed...
Screenshot:
https://imgur.com/a/x55gW