macOS Monterey failing to start vagrant box?

Solution 1:

Re-install whatever version of VirtualBox you are using to get the host-only adapter in place again.

The other answers here are focusing on other issue — where VirtualBox is failing to start in headless mode as described in this other question — but your error is clearly different and something I ran into myself. Note this error you are getting:

VBoxManage: error: Failed to create the host-only adapter

I had this error as well. And the only way I solved it is to reboot my MacBook, and then reinstall VirtualBox again.

I believe this happens when one updates VirtualBox, and then that “System Preferences” prompt comes up. I believe it stops the process of installing the host-only adapter so you basically have to reboot and reinstall VirtualBox again.

To confirm the host-only adapter is indeed in place, launch the VirtualBox GUI application and then click on “Tools” which is the top menu item on the left; you should see a vboxnet0 adapter as shown in the screenshot below.

That vboxnet0 is the host-only adapter. And if it is there, you should be able to do a vagrant up and your machine should start. But then again — as said at the outset — there is another issue with Vagrant and VirtualBox that is addressed in that other SuperUser thread.