環境 HostOS: MacOS 10.10.2 Getst: CentOS 7.2 vagrant: 1.8.1 症状 一度仮想環境を終了した後に, 再びvagrant upで再起動を行った際に, shared folderのmountに失敗したとのログが表示される. 起動したゲストOSへはSSHでログインすることができる. Failed to mount folders in Linux guest. This is usually because the "vboxsf" file system is not available. Please verify that the guest additions are properly installed in the guest and can work properly. The command attempted was: mou