vagrant up したら "Guest Additions Version" とに関するエラーが出た時のメモ

The guest additions on this VM do not match the installed version of
VirtualBox! In most cases this is fine, but in rare cases it can
cause things such as shared folders to not work properly. If you see
shared folder errors, please update the guest additions within the
virtual machine and reload your VM.

Guest Additions Version: 4.2.0
VirtualBox Version: 4.3

こんなエラーが出る。 調べた結果、Vagrantのプラグインを入れればいいらしい。

$ vagrant plugin install vagrant-vbguest


config.vbguest.auto_update = true

その後、vagrant up / vagrant reload。