I occasionally run into the following error when trying to vagrant up:
NFS is reporting that your exports file is invalid. Vagrant does this check before making any changes to the file. Please correct the issues below and execute "vagrant reload": exports:2: path contains non-directory or non-existent components: /Users/macpro/code/wip-HOSSUP-3518 exports:2: no usable directories in export entry exports:2: using fallback (marked offline): /
I've been able to replicate the error by deleting a VM from my development directory. It seems that Vagrant must verify your /etc/exports file against your available VMs when running any vagrant up. If you routinely clone and delete VMs, you'll probably run into this issue.
Last week I documented a workaround on Stackoverflow. But it looks like it might be even simpler:
vagrant halt // Yes, the VM is running, despite death rattle featured above. rm -rf /etc/exports // Remove the exports file. vagrant up
Be sure to halt before attempting this. vagrant reload will not work. Vagrant recreates /etc/exports on the next vagrant up.