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: 
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.
One can't simply destroy his/her system by issuing `rm -rf /` as root. Initially, the command will be issued under fail-safe mode, which will restrict the usage of `rm` on `/` but even with `--no-preserve-root` as an argument, the running system will not permit the removal of running processes from the disk; however, the rest of the programs and files will be removed, leaving an unusable system with (almost) no programs to run! Please check the screenshots tarred here, the command was issued in Arch Linux in Virtual Box: <http://bit.ly/q9CsA4>