1 First steps Please see chapter 14, Known limitations, page 181 for additional remarks. 2. If you have the Guest Additions installed and they support automatic resizing, the Guest Additions will automatically adjust the screen resolution of the guest operating system. For example, if you are running a Windows guest with a resolution of 1024x768 pixels and you then resize the VM window to make it 100 pixels wider, the Guest Additions will change the Windows display resolution to 1124x768. Please see chapter 4, Guest Additions, page 53 for more information about the Guest Addi- tions. 3. Otherwise, if the window is bigger than the VM’s screen, the screen will be centered. If it is smaller, then scroll bars will be added to the machine window. 1.8.6 Saving the state of the machine When you click on the “Close” button of your virtual machine window (at the top right of the win- dow, just like you would close any other window on your system), VirtualBox asks you whether you want to “save” or “power off” the VM. (As a shortcut, you can also press the Host key together with “Q”.) The difference between these three options is crucial. They mean: • Save the machine state: With this option, VirtualBox “freezes” the virtual machine by completely saving its state to your local disk. When you start the VM again later, you will find that the VM continues exactly where it was left off. All your programs will still be open, and your computer resumes operation. Saving the state of a virtual machine is thus in some ways similar to suspending a laptop computer (e.g. by closing its lid). • Send the shutdown signal. This will send an ACPI shutdown signal to the virtual machine, which has the same effect as if you had pressed the power button on a real computer. So long as the VM is running a fairly modern operating system, this should trigger a proper shutdown mechanism from within the VM. • Power off the machine: With this option, VirtualBox also stops running the virtual ma- chine, but without saving its state. Warning: This is equivalent to pulling the power plug on a real computer without shutting it down properly. If you start the machine again after powering it off, your operating system will have to reboot completely and may begin a lengthy check of its (virtual) system disks. As a result, this should not normally be done, since it can potentially cause data loss or an inconsistent state of the guest system on disk. 22