seamless mode fails while starting a snapshot

[Paolo Virtual]

When (re)starting a snapshot that was taken while in seamless mode, the seamless mode does not work from time to time (but the default window-mode is entered). This also happens when we explicitly start in seamless mode doing both:

• VBoxManage setextradata "GUI/Seamless" on, as well as

• VirtualBox --startvm <name> --seamless

One way to (quite) deterministically reproduce this error is on a Windows XP host, to shut down Windows while VirtualBox is still running in seamless mode and rebooting Windows and starting the VM again.

But this problem is not only limited to Windows XP hosts, it also appears within Windows 7 and Linux hosts. However, it is unclear when exactly it happens. Is there any workaround to *really* force the machine to startup in seamless mode? Are there any files which remain in an unclean state when VirtualBox is killed, instead of powered down via the API?

[Dsen]

First of all, I should warn that 'seamless' mode is quite depending on Guest Additions notifications. When starting VBox GUI for particular VM, it always uses 'normal' mode by default even if last mode was 'seamless' because GUI do not actually knows if 'seamless' mode is supported. The same is for situation when 'GUI/Seamless' flag was set or '--seamless' attribute was used.

Only when/if the Guest Additions notifies the GUI about 'seamless' mode is supported and there was a request to enter 'seamless' mode (flag or attribute) - VM will try to enter 'seamless' mode. When user restores VM from saved state GUI follows the same rule but that sequence happens much more faster (a couple of seconds usually).

Besides that, 'GUI/Seamless' flag becoming set when VM correctly powered off (process not just killed, but VM is powered off or guest system shutdowned). We can make this flag becoming set just when VM entered 'seamless' mode to avoid such data loss.

[Paolo Virtual]

The point is that I explicitely set the flag with 'VBoxManage setextradata "GUI/Seamless" on' before starting the machine. So I should be on the safe side, regardless if the VM was powered off or just killed.

When I kill the VM with the task manager and set the flag as above, the seamless mode is reentered correctly.

But when I shut down Windows XP, restart XP, set the flag as above and restart the VM it does not reenter seamless mode.

Could killing VBoxSVC (via the Windows XP shutdown) be the cause? Are there any locks etc. which remain after shutting down XP, but not after just killing VirtualBox?

[aeichner]

Please reopen if still relevant with a recent VirtualBox release.