Reboot your system first so that it's all up to date.
Now, download the [Guest Additions](http://download.virtualbox.org/virtualbox/) as an `.iso` file and mount it from VirtualBox's menu. Then in the guest machine do the following (this will also reboot your system):
``` bash
sudo mkdir -p /mnt/cdrom
sudo mount -t iso9660 -o ro /dev/cdrom /mnt/cdrom
cd /mnt/cdrom
sudo sh VBoxLinuxAdditions.run
sudo reboot
```
**Note:** For each kernel update you will need to rebuild the Virtualbox Modules. So simply remount the ISO and run the instructions again.
By default, the virtualbox modules for those virtualbox features are not loaded/enabled, therefore the features simply do not work if selected in the Guest.
If you want that this features to work properly automatically, without starting the corresponding VBoxClient yourself, you can use xdg to autostart VBoxClient enabling the features.
/usr/bin/VBoxClient-all:
``` bash
#!/bin/sh
## @file
# Start the Guest Additions X11 Client
#
#
# Copyright (C) 2007-2012 Oracle Corporation
#
# This file is part of VirtualBox Open Source Edition (OSE), as
# available from http://www.virtualbox.org. This file is free software;
# you can redistribute it and/or modify it under the terms of the GNU
# General Public License (GPL) as published by the Free Software
# Foundation, in version 2 as it comes in the "COPYING" file of the
# VirtualBox OSE distribution. VirtualBox OSE is distributed in the
# hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
#
# Sanity check: if non-writeable PID-files are present in the user home
# directory VBoxClient will fail to start.
for i in $HOME/.vboxclient-*.pid; do
test -w $i || rm -f $i
done
if ! test -c /dev/vboxguest 2>/dev/null; then
# Do not start if the kernel module is not present.
notify-send "VBoxClient: the VirtualBox kernel service is not running. Exiting."
elif test -z "${SSH_CONNECTION}"; then
# This script can also be triggered by a connection over SSH, which is not
# what we had in mind, so we do not start VBoxClient in that case. We do
# not use "exit" here as this script is "source"d, not executed.
/usr/bin/VBoxClient --clipboard
/usr/bin/VBoxClient --checkhostversion
/usr/bin/VBoxClient --display
/usr/bin/VBoxClient --seamless
/usr/bin/VBoxClient --draganddrop
fi
```
You need to make the file executable in order for this to work:
``` bash
sudo chmod +x /usr/bin/VBoxClient-all
```
/etc/xdg/autostart/vboxclient.desktop:
``` bash
[Desktop Entry]
Type=Application
Encoding=UTF-8
Version=1.0
Name=vboxclient
Name[C]=vboxclient
Comment[C]=VirtualBox User Session Services
Comment=VirtualBox User Session Services
Comment[it]=Servizi di sessione utente di VirtualBox
Download the latest [VirtualBox Installer](https://www.virtualbox.org/wiki/Linux_Downloads) - [direct link](http://download.virtualbox.org/virtualbox/5.1.16/VirtualBox-5.1.16-113841-Linux_amd64.run) (5.1.16) right click link and Save As.