Configure VirtualBox Shared Folders for Linux Guest OS

Step by step instruction for VirtualBox shared folders set up

Page content

To configure VirtualBox shared folders in Linux Guest OS, follow these steps:

virtual box shared folders config window

1. Install VirtualBox Guest Additions

Guest Additions must be installed in the guest OS to enable shared folder support:

  • Start the guest.
  • In VirtualBox menu, select:
Devices > Insert Guest Additions CD Image

Insert Guest Additions CD Image screenshot

  • Open a terminal in the guest, mount the CD if necessary, and run the installer:
sudo sh /media/$USER/VBox_GAs_*/VBoxLinuxAdditions.run

  • Reboot the guest after installation.

  • Add your user to the vboxsf group in the guest (this is crucial for access permissions):

sudo usermod -aG vboxsf $(whoami)

` Reboot or log out/in for group changes to take effect.

2. Configure Shared Folder in VirtualBox Manager on the Host

  • Right-click your VM and go to:
Settings > Shared Folders
  • Click the Add Shared Folder button.
  • Set the following:
    • Folder Path: The folder on your Linux host to be shared.
    • Folder Name: The name to reference in the guest (e.g., share).
    • Optionally check Auto-mount so it mounts automatically at boot.
    • Optionally check Make Permanent for persistent share.

3. Mount the Shared Folder in the Linux Guest

If Auto-mount was enabled, VirtualBox will mount the shared folder automatically, typically at /media/sf_ (e.g., /media/sf_share) and with group access for vboxsf.

If you want to mount it manually or to a custom location:

  • Create a mount point:
mkdir ~/host_share
  • Mount using:
sudo mount -t vboxsf  ~/host_share

Mount Shared Folder automatically on boot

On a Linux guest, the recommended approach is to add an entry for the shared folder in the guest’s /etc/fstab. This ensures the folder is mounted each time the system boots.

Open /etc/fstab with a text editor as root:

sudo nano /etc/fstab

Add a line like this, replacing sharename and /home/youruser/host_share with your desired path (e.g., /mnt/shared):

sharename   /home/youruser/host_share   vboxsf  defaults  0   0

The sharename is as defined in VirtualBox Shared Folders settings.

Create the mount point (if it doesn’t exist):

mkdir -p /home/youruser/host_share

Mount all filesystems or reboot to test:

sudo mount -a

Check that your shared folder is now accessible.

Access, Permissions & Troubleshooting

  • The shared folder will be owned by root:vboxsf inside the guest.
  • Make sure your guest user is in the vboxsf group (id $USER to check).
  • If you experience permission issues, make sure you are in the vboxsf group and that you log out/in (or reboot) after adding yourself to the group.
  • For more complex needs or for dynamic/conditional mounting, you can also utilize a systemd automount unit, but /etc/fstab is the most straightforward and robust for VirtualBox shared folders on Linux.

This approach will ensure your VirtualBox shared folder mounts automatically at every system startup.

VirtualBox can’t operate in VMX root mode.

If you get the following error which blames KVM kernel module

VBoxManage: error:
VirtualBox can't operate in VMX root mode.
Please disable the KVM kernel extension, recompile your kernel and reboot
(VERR_VMX_IN_VMX_ROOT_MODE)

VBoxManage: error:
Details:
code NS_ERROR_FAILURE (0x80004005),
component ConsoleWrap, interface IConsole

Do the following at your own risk. You can try to overcome this error on Ubuntu 24.04 by disabling it temporarily, just make sure noone is using kvm at the moment:

lsmod | grep kvm
lsof | grep kvm
sudo modprobe -r kvm_intel

You can try to disable and recompile if you wish too, and if you use VirtualBox a lot

Check if kvm is loaded (should be the case when getting the VirtualBox error):

lsmod | grep kvm

To check if kvm is currently in use:

lsof | grep kvm

If there is no output, kvm is not being used and the kernel module can be safely unloaded:

sudo rmmod kvm_intel # or kvm_amd on AMD CPUs
sudo rmmod kvm

This will only unload the kernel modul for the current session. To disable kvm on boot you need to blacklist it and update the initramfs. Add this to /etc/modprobe.d/blacklist-kvm.conf:

blacklist kvm
blacklist kvm_intel   # or kvm_amd

Update initramfs and reboot:

sudo update-initramfs -u
sudo reboot