data in guest and host

[freewind]

Hello.
Sorry for my english.
I have last VBOX with GA. Host and Guest WinXP.
In Guest I need to run some program for change the data and time to past. But this programms not work, becouse Guest OS is rapidly sync data/time with host. How I can resolve this problem?
Thank you.

[TerryE]

You can use VBoxManage modifyvm uuid/name -biossystemtimeoffset msec. Just do the math and convert your delta time into milliseconds. If necessary you can put this in a script immediately before the VBoxManage startvm command. This will allow you to fix the start time within a few seconds.

[freewind]

Thank you.
But, can I simply disable data and time sync between guest and host? I need different data for some programms that I run in VM. I use dater - simply programm to set data to past, before run basic programm. This very comfortable.

[TerryE]

IIRC, the clock of the guest is initialised by the guest BIOS from the host time at startup. Thereafter it is kept in sync with the Guest Additions timer driver, so just don't bother to load GA and you should be able to reset the time within the guest.

[ghr]

So my conclusion (as well as my experience) is: installing GA makes the VBox command VBoxManage modifyvm uuid/name -biossystemtimeoffset msec useless... Right ?

[TerryE]

AFAIK, the GA driver honours the biossystemtimeoffset parameter.

[TerryE]

Oops, cancel last. The code for the synchronisation is in vboxadd-timesync.c. This basically runs a loop where it compares the host time (requested from the HCGC interface) to the current gettimeofday and then converges these by 5ms per 10s unless the delta is >5 mins in which case it just resets the time to the host time as a bang.

I would have expected an offset in this calculation based on the biossystemtimeoffset parameter accessed through the BIOS, but it doesn't so it looks as if you are correct.

I've updated http://www.virtualbox.org/ticket/2107 accordingly.

[vbox4me2]

High 5

[vbox4me2]

Here's a hack, tested and working.

Locate VBoxGuest.sys in C:\WINDOWS\system32\drivers
Open it with a hexeditor (tiny hexer) and locate the word:
"ZwSetSystemTime", then zero out the first character "Z", reboot the guest(VM) and have your VM live in the past or future.

Ps. the security logs also don't get flooded anymore with 520 events.

[Rodriguin81]

Hello, I could not make the change in ..sys. I not understand "then zero out". Can you explain that it means, please?

Thanks in advance

[TerryE]

He means replace it with a zero byte "\0x00". You can do this with any hex editor. That way the symbol is changed from "ZwSetSystemTime" to "" which does not resolve so the call to set the time fails silently.

[Rodriguin81]

OK, I only replace the "Z" character for NULL or 0x00.. and no good result (the guest no boot, but no problem).
Tomorrow i'll try to change all string for "" and tell you for results jejeje

[i_saw_drones]

Here's a hack, tested and working.

Locate VBoxGuest.sys in C:\WINDOWS\system32\drivers
Open it with a hexeditor (tiny hexer) and locate the word:
"ZwSetSystemTime", then zero out the first character "Z", reboot the guest(VM) and have your VM live in the past or future.

Ps. the security logs also don't get flooded anymore with 520 events.

Hi there,
Thanks a lot for this, been looking everywhere for a solution.
However, I have also tried this replacement method directly in hex, by replacing the "Z" with a null and also a space, as well as replacing the whole function name with nulls but with no luck. My vista guest just falls over when trying to use the modified version (based on GA 2.1.4).
Sorry to be a pain, but could you please be so kind as to tell me exactly what you did to have this work?

Thank you very much.

[vbox4me2]

Nothing personal but if you can't get this to work then this hack is not for you. This should be resolved by the devellopment team so file a ticket or compile the OSE yourself. As you have seen the Host can crash if done wrong.