Bidirectional clipboard sharing is enabled default in the VirtualBox VMs. There are security reasons. For Whonix-Gateway ™, one directional clipboard sharing from host to Whonix-Gateway ™ is not insecure.
To change clipboard sharing:
1) Power off the virtual machine.
2) Go to VirtualBox machine settings → General → Advanced → Shared Clipboard → .
3) Power on the virtual machine again.
If you are using a Whonix-Custom-Workstation ™ you need to do this manually, please click on expand on the right.
Two options. Automatic mounting or manual mounting. Automatic mounting is described below. For automatic mounting see https://www.virtualbox.org/manual/ch04.html#sharedfolders - This is VirtualBox question, unspecific to Whonix as per Free Support Principle.
1) Install VirtualBox guest additions inside the VM. 
2) Add the user supposed to use shared folders from inside the VM to group
sudo addgroup user vboxsf
3) Reboot required to make group changes take effect.
4) Follow instructions below.
1) Go to the shared folder settings of your virtual machine.
VirtualBox → right click your virtual machine →
2) Click the icon that looks like a folder with a
+ in the upper right.
Folder Path → Navigate to the folder you want to share.
Folder Name → Type:
You could also use a folder name other than
shared but using
shared is recommended so you have the same name and can use the example documented below.
Do not use
share (without the trailing
Read-only if you don't want to write to that folder from within the guest.
Mount Point → Leave as is. No changes. Leave empty. 
Make Permanent. 
OK to close shared folder dialog.
OK to VirtualBox settings.
12) The process is now complete.
13) You can now start using the shared folder.
VirtualBox shared folders can be found inside the virtual machine in folder
By default VirtualBox uses the prefix
For example if you named your folder
shared the shared folder will become
/media/sf_shared. You can open it using a file manager such as Thunar. Or using the the command line.
Installed by Default
Beginning from Whonix ™ 10 and above, VirtualBox Guest Additions are already installed by default. (Package virtualbox-guest-x11 from Debian's apt repository.)
For technical information:
See blog post, Installing VirtualBox Guest Addition by Default?
Old instructions for Ubuntu Precise
Moved to Ubuntu Tips.
Installation from VirtualBox CD
Discouraged until make vbox-disable-timesync compatible with guest additions from virtualbox CD gets implemented.
- For file exchange with Whonix ™ without installing guest additions, see File Transfer.
- To get a higher screen resolution without installing guest additions, see VirtualBox/Higher Screen Resolution without installing VirtualBox Guest Additions
- To get mouse integration without installing guest additions, use USB tablet in VirtualBox settings. Recommended against, because it requires adding USB controller to VirtualBox. (VirtualBox → Right click on Virtual Machine → Settings → System → Enable absolute pointing device)
Temporary disable Guest Additions
This solution is incomplete! In case you want to temporarily disable VirtualBox guest additions, you can try this. A safer solution would be to uninstall them.
Find out which VirtualBox kernel modules are load.
Create a new config file for module blacklisting.
sudo nano /etc/modprobe.d/vbox.conf
blacklist vboxvideo blacklist vboxsf blacklist vboxguest
Safe and reboot. Done.
- to disable clipboard sharing, such as preventing accidentally copying something (non-)anonymous and pasting it in its (non-)anonymous counter part (browser etc.), which would lead to identity correlation.
- Since Whonix-Gateway ™ is not supposed to be used as a workstation. No internet facing client application are being used there. Whatever "leaked" to Whonix-Gateway ™ stays there and since conceptually users do not use browsers or similar on Whonix-Gateway ™, it cannot leak anywhere.
- Because otherwise you cannot change VirtualBox VM settings.
- Required. Quote https://www.virtualbox.org/manual/ch04.html#sharedfolders
With the shared folders feature of Oracle VM VirtualBox, you can access files of your host system from within the guest system. This is similar to how you would use network shares in Windows networks, except that shared folders do not require networking, only the Guest Additions.
- If not available, upgrade VirtualBox.
Alternatively you could also chose folder
/home/user/shared. That folder by VirtualBox default would be owned by owner
Make Permanentif you want this setting to persist after restart of the virtual machine. Otherwise this setting be temporary.
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