If your host OS is Windows with a Linux flavor as a guest OS, here is a quick reminder of the steps to proceed to install or update the current VirtualBox guest additions.
The VirtualBox guest additions are located in the VBoxGuestAdditions ISO image which can be found in C:\Program Files\Oracle\VirtualBox
To install them, load this ISO image into your virtual CD/DVD drive and your OS guest should make it available through a mount point. Make a local copy of its content into a folder and launch the following command as root :
Verifying archive integrity… All good.
Uncompressing VirtualBox 4.1.22 Guest Additions for Linux………
VirtualBox Guest Additions installer
Removing installed version 4.1.16 of VirtualBox Guest Additions…
Removing existing VirtualBox DKMS kernel modules …done.
Removing existing VirtualBox non-DKMS kernel modules …done.
Building the VirtualBox Guest Additions kernel modules …done.
Doing non-kernel setup of the Guest Additions …done.
You should restart your guest to make sure the new modules are actually used
Installing the Window System drivers
Installing X.Org Server 1.7 modules …done.
Setting up the Window System to use the Guest Additions …done.
You may need to restart the hal service and the Window System (or just restart
the guest system) to enable the Guest Additions.
Installing graphics libraries and desktop services components …done.
Three services should be present in /etc/init.d :
After the install/upgrade of VirtualBox guest additions, reboot your guest OS to make the upgrade take effect.
For more information : Installing VirtualBox guest additions