- Changing the virtual harddisk UUID (.vdi)
VBoxManage internalcommands sethduuid /VirtualMachine/virtualmachine.vdi
- Resizing the virtual harddisk
VBoxManage modifyhd virtualmachine.vdi --resize SIZE_MB
- Disable time synchronization
VBoxManage setextradata LHBU "VBoxInternal/Devices/VMMDev/0/Config/GetHostTimeDisabled" "1"
Unrecommended workaround is:
Guest Windows: go to Services, find VirtualBox Guest Additions service and stop it. You will find that time synch is no longer working, but I'm not sure whether other functionalities regarding virtual box - host integration are affected or no.
Guest Linux: /etc/init.d/vboxadd-timesync stop
Disclaimer! Never tried the linux version, found it during googling.