VirtualBox snapshots

Question

When VirtualBox restores a snapshot, is that like coming back from hibernation?

Answer 1

A snapshot saves exactly what the virtual machine was doing in a certain point in time.

• If it is powered off when you take the snapshot, later when you revert to it, the machine will still be powered off and require a normal startup.
• If the machine is running when you take the snapshot, and has some applications running, later when you revert to it, the machine will be exactly like when you took the snapshot. Possibly with the exception of the system clock, that still synchronizes with the real time on your host machine.

It is like hibernation in the sense that the state of the operating system and the software running on it is saved to a hard drive.
It is different because the guest OS itself is not in charge of saving and restoring that state, your Virtualbox software running on the host OS is. Because of that it works better and faster.

Answer 2

Restoring a snapshot reverts the OS to the exact state that it was in when the snapshot was taken.

From the Virtualbox documentation:

You can restore a snapshot by right-clicking on any snapshot you have taken in the list of snapshots. By restoring a snapshot, you go back (or forward) in time: the current state of the machine is lost, and the machine is restored to exactly the same state as it was when then snapshot was taken

...

Finally, if you took a snapshot while the machine was running, the memory state of the machine is also saved in the snapshot (the same way the memory can be saved when you close the VM window) so that when you restore the snapshot, execution resumes at exactly the point when the snapshot was taken.