Vagrant requires privileged access to the VM, either using config.ssh.username = "root"
, or more commonly, via sudo
. The Bento Ubuntu boxes currently configure it directly to /etc/sudoers.
I don't know what ansible's sudo_user does or means, but I guess your provisioning is overriding /etc/sudoers. In this case you really need to ensure you don't lose Vagrant's sudo access to the VM. Or build your own base box which uses sudoers.d.
As a side note, if you create a /etc/sudoers.d/ file, you should also set it's mode to 0440 or at least some older sudo versions refuse to apply it.