Virtual BoxのGuest Additionsのバージョンを合わせることができない

Question

【起こっている問題】
vagrant upをして仮想環境に入る時に、下記のエラーが発生します。

==> default: Attempting graceful shutdown of VM...
==> default: Clearing any previously set forwarded ports...
==> default: Clearing any previously set network interfaces...
==> default: Preparing network interfaces based on configuration...
    default: Adapter 1: nat
==> default: Forwarding ports...
    default: 3000 (guest) => 8000 (host) (adapter 1)
    default: 22 (guest) => 2222 (host) (adapter 1)
==> default: Running 'pre-boot' VM customizations...
==> default: Booting VM...
==> default: Waiting for machine to boot. This may take a few minutes...
    default: SSH address: 127.0.0.1:2222
    default: SSH username: vagrant
    default: SSH auth method: private key
    default: Warning: Connection aborted. Retrying...
==> default: Machine booted and ready!
[default] GuestAdditions versions on your host (5.0.30) and guest (5.0.18) do no
t match.
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
 * base: ftp.tsukuba.wide.ad.jp
 * extras: ftp.tsukuba.wide.ad.jp
 * updates: ftp.tsukuba.wide.ad.jp
Package gcc-4.8.5-11.el7.x86_64 already installed and latest version
Package binutils-2.25.1-22.base.el7.x86_64 already installed and latest version
Package 1:make-3.82-23.el7.x86_64 already installed and latest version
Package 4:perl-5.16.3-291.el7.x86_64 already installed and latest version
Package bzip2-1.0.6-13.el7.x86_64 already installed and latest version
Nothing to do
Copy iso file C:\Program Files\Oracle\VirtualBox\VBoxGuestAdditions.iso into the
 box /tmp/VBoxGuestAdditions.iso
mount: /dev/loop0 is write-protected, mounting read-only
Installing Virtualbox Guest Additions 5.0.18 - guest version is 5.0.18
Verifying archive integrity... All good.
Uncompressing VirtualBox 5.0.18 Guest Additions for Linux............
VirtualBox Guest Additions installer
You appear to have a version of the VBoxGuestAdditions software
on your system which was installed from a different source or using a
different type of installer.  If you installed it from a package from your
Linux distribution or if it is a default part of the system then we strongly
recommend that you cancel this installation and remove it properly before
installing this version.  If this is simply an older or a damaged
installation you may safely proceed.

Do you wish to continue anyway? [yes or no]

Cancelling installation.
An error occurred during installation of VirtualBox Guest Additions 5.0.18. Some
 functionality may not work as intended.
In most cases it is OK that the "Window System drivers" installation failed.
Redirecting to /bin/systemctl start  vboxadd.service
Failed to start vboxadd.service: Unit not found.
==> default: Checking for guest additions in VM...
==> default: Mounting shared folders...
    default: /vagrant => C:/Users/m-hori/VM/centos7/sample
Vagrant was unable to mount VirtualBox shared folders. This is usually
because the filesystem "vboxsf" is not available. This filesystem is
made available via the VirtualBox Guest Additions and kernel module.
Please verify that these guest additions are properly installed in the
guest. This is not a bug in Vagrant and is usually caused by a faulty
Vagrant box. For context, the command attempted was:

mount -t vboxsf -o uid=1001,gid=1001 vagrant /vagrant

The error output from the command was:

mount: unknown filesystem type 'vboxsf'

上記内容に関して調べてみたところ

 GuestAdditions versions on your host (5.0.30) and guest (5.0.18) do no
t match.

の部分を解消する方法を見つけました。
参照：http://qiita.com/ozawan/items/9751dcfd9bd4c470cd82

vagrant plugin install vagrant-vbguest

としてvagrant-vbguestというプラグインを入れて

vagrant vbguest --status

とすると

[default] GuestAdditions versions on your host (5.0.30) and guest (5.0.18) do no
t match.

とのことで、これを解消するために

vagrant vbguest

としてみましたが、

[default] GuestAdditions versions on your host (5.0.30) and guest (5.0.18) do no
t match.
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
 * base: ftp.tsukuba.wide.ad.jp
 * extras: ftp.tsukuba.wide.ad.jp
 * updates: ftp.tsukuba.wide.ad.jp
Package gcc-4.8.5-11.el7.x86_64 already installed and latest version
Package binutils-2.25.1-22.base.el7.x86_64 already installed and latest version
Package 1:make-3.82-23.el7.x86_64 already installed and latest version
Package 4:perl-5.16.3-291.el7.x86_64 already installed and latest version
Package bzip2-1.0.6-13.el7.x86_64 already installed and latest version
Nothing to do
Copy iso file C:\Program Files\Oracle\VirtualBox\VBoxGuestAdditions.iso into the
 box /tmp/VBoxGuestAdditions.iso
mount: /dev/loop0 is write-protected, mounting read-only
Installing Virtualbox Guest Additions 5.0.18 - guest version is 5.0.18
Verifying archive integrity... All good.
Uncompressing VirtualBox 5.0.18 Guest Additions for Linux............
VirtualBox Guest Additions installer
You appear to have a version of the VBoxGuestAdditions software
on your system which was installed from a different source or using a
different type of installer.  If you installed it from a package from your
Linux distribution or if it is a default part of the system then we strongly
recommend that you cancel this installation and remove it properly before
installing this version.  If this is simply an older or a damaged
installation you may safely proceed.

Do you wish to continue anyway? [yes or no]

Cancelling installation.
An error occurred during installation of VirtualBox Guest Additions 5.0.18. Some
 functionality may not work as intended.
In most cases it is OK that the "Window System drivers" installation failed.
Redirecting to /bin/systemctl start  vboxadd.service

となりうまくインストールが出来ません。

 GuestAdditions versions on your host (5.0.30) and guest (5.0.18) do no
t match.

となっているエラーをまずは解決したいのですが、詳しい方、教えていただけませんでしょうか。

Answer 1

VirtualBox 本体（Guest Additions ではなく）をバージョンアップしてみてください。

私も Mac で同じような現象に遭遇したことがあり、原因は VirtualBox のバージョンが古すぎることでした。