Question: If you are root, and you issue 

```
rm -rf / 

```

Then how far can the command go? Can you recover data from this kind of an action? Even after the binaries are gone, would the running processes still be active? What would it take to make the same physical machine boot again? What files would you need to restore to make this happen?

I could try this on a VM and see, but I want to know the rationale behind what to expect if I do this.

Answer: 
This command does nothing, at least on the OS I use (Solaris) with which this security feature was first implemented:

```
# rm -rf /
rm of / is not allowed

```

On other \*nix, especially the Linux family, if a recent enough Gnu rm is provided, you would need to add the `--no-preserve-root` option to enable the command to complete (or at least start).

How far would this command go is undefined. It depends on plenty of more or less unpredictable events. Generally, processes can run even after their binaries have been removed.
Even with jlliagre's excellent answer, remember this is still a pretty dangerous thing to do. **Always** double check where you are before doing things like `rm -rf`. It would be catastrophic if you were to do `rm -rf *` while in the /usr directory, for instance.

As to the rest of your questions, what you can recover pretty much depends on your backup procedures. In most \*nix systems there is no simple way to recover files and directories once they have been deleted. Unlike the old DOS days where files were often still on the disk after a delete was performed, most systems these days do things that make recovery very difficult. This is one of the reasons that data recovery services are so expensive.

If you are using a VM, I recommend doing snapshots from time to time at the very least. But nothing can beat following a good backup plan.