（追記）Vagrant 1.4.0 で治ってるのを確認しました
Mavericks です。
$ vagrant up Bringing machine 'default' up with 'virtualbox' provider... [default] Importing base box 'precise64'... [default] Matching MAC address for NAT networking... [default] Setting the name of the VM... [default] Clearing any previously set forwarded ports... [default] Creating shared folders metadata... [default] Clearing any previously set network interfaces... [default] Preparing network interfaces based on configuration... [default] Forwarding ports... [default] -- 22 => 2222 (adapter 1) [default] Booting VM... [default] Waiting for machine to boot. This may take a few minutes... [default] Machine booted and ready! [default] 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 [default] Configuring and enabling network interfaces... [default] Mounting shared folders... [default] Exporting NFS shared folders... Preparing to edit /etc/exports. Administrator privileges will be required... WARNING: Improper use of the sudo command could lead to data loss or the deletion of important system files. Please double-check your typing when using sudo. Type "man sudo" for more information. To proceed, enter your password, or type Ctrl-C to abort. Password: [default] Mounting NFS shared folders... The following SSH command responded with a non-zero exit status. Vagrant assumes that this means the command failed! mount -o 'vers=3,udp' 192.168.2.1:'/Users/oogatta/hogehoge' /vagrant Stdout from the command: Stderr from the command: stdin: is not a tty mount.nfs: requested NFS version or transport protocol is not supported
ファック！これだった…。
config.vm.synced_folder ".", "/vagrant", nfs: true
これを
config.vm.synced_folder "./", "/vagrant/", nfs: true
こうしてディレクトリ名の末尾にスラッシュ付けたら治った。これ、すごく切ない。