Here are some issues you will face when playing around with Vagrant and how to fix them:
1. Cannot install plugin
Remove ~/.vagrant.d directory before re-installing vagrant.
2. Your VM has become "inaccessible." Unfortunately, this is a critical error with VirtualBox that Vagrant can not cleanly recover from. Please open VirtualBox and clear out your inaccessible virtual machines or find a way to fix them.
Remove .vagrant file.
3. Cannot run a vm with Vitualbox:
Enable VT-x feature in your machine's BIOS.