HOW-TO Reset a VM user password

If you forget the user's password for a VM, the simplest solution is to restart the VM into single user mode.

Originally the fix found on this thread on AskUbuntu

Reboot the VM and, during the GRUB splash-screen, hit ESC
With the list of options available, hit the e key and, in the editor presented, add single at the end of a line similar to this one:
```
linux /boot/vmlinux-3.13...-generic root=UUID=<uuid> ro
```
so that it looks like this:
```
linux /boot/vmlinux-3.13...-generic root=UUID=<uuid> ro single
```
you will be presented with a console and the root prompt (#): use the passwd command to change your user's password:
```
# passwd marco
```

If you can't even remember which user(s) were configured, the easiest way is to ls /home - or use the following:

# cat /etc/passwd | grep -e "/bin/bash$" | cut -f1 -d: | sort

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