This simple tutorial shows how to install Virtualbox Guest Additions in Ubuntu based systems, e.g., Linux Mint, Zorin OS and Elementary OS, with fix or workaround for common issues.

Guest Additions is a set of device drivers and system applications to install in Guest OS. It’s useful when you try to share folder and/or clipboard between guest and host, enable USB support etc. Installing the software suite is easy via a menu option. However, it might not function in some cases.

Install Guest Additions in the Normal Way

Firstly, start and login the Guest OS. Then go to VM menu “Devices -> Insert Guest Additions CD image“.

Usually, a pop-up dialog will open and prompt whether to run autorun script or not. Just click “Run” and it starts to install the guest additions after you typing user password in authentication dialog.

After installation, the additions will function in next boot of the Guest OS.

[Workaround] Unable to insert the virtual optical disk:

Sometimes it outputs an error “Unable to insert the virtual optical disk … into the machine …” when you click on the menu option in VM (VirtualBox Machine).

It happens in my case when trying to install the additions in Elementary OS 6. And it will pop-up an error dialog:

Don’t know why but do following steps will fix the issue in next Guest boot:

1.) Power off the Guest OS, then go to its Settings page. Under the Storage settings, remove the attached iso under Controller:IDE.

2.) Next add new optical drive, and click “Leave Empty” in the select dialog.

After saving the changes, start the Guest OS and try to install the additions again.

Manually Download & Install Guest Additions:

Nothing happens when clicking ‘Insert Guest Additions CD image’ option? You can download the iso, mount it, and install the Guest Additions manually.

1.) Firstly start the VirtualBox Machine, download the iso image for your VirtualBox edition, usually “VBoxGuestAdditions_x.x.xx.iso”, from the link button below:

2.) Next open the Downloads folder, right-click or (double-click) on the file and select to mount the iso image.

The dialog should pop-up allows you to select “Run” to install the additions. If not, go to the mounted folder from the left pane in file manager. Right-click on blank area and select ‘Open in Terminal‘ to open a terminal window and navigate to the directory automatically.

When terminal opens, run the .run installer manually via command:

sudo ./VBoxLinuxAdditions.run

That’s all. Enjoy!

This tutorial shows how to mount the VirtualBox virtual disk image in Ubuntu, so you can access the Guest OS file system with read and write permission, if it does not boot.

After misconfigured my VirtualBox Guest OS, it does not longer work. I know how to correct the issue to make it boot again, but firstly accessing to the file system is required!

Since the VBox user manual does not work, here’s what I did in Ubuntu 20.04 host with VirtualBox 6.1.x:

1.) Firstly open terminal from system application launcher. When it opens, run command:

vboximg-mount --list

vboximg-mount is a utility to make VBox disk images available to the host. With --list, it list all Disk Images as well as the UUID.

In the case, I have all Guest OSes on single Disk Image (.vdi). And the uuid is: “3db5fd91-fd56-46af-a2d2-98cd62b05ea3”

2.) Next perform a FUSE mount of the virtual disk image:

• First create a folder as mount point, vbox_sysdisk for instance:

  mkdir vbox_sysdisk

• Then mount it via command (remember to change the UUID to yours):

  vboximg-mount -i 3db5fd91-fd56-46af-a2d2-98cd62b05ea3 -o allow_root vbox_sysdisk

NOTE: You may need to edit the “/etc/fuse.conf” to make the -o allow_root flag work. To do so, run command sudo gedit /etc/fuse.conf and enable (remove # at its beginning) “user_allow_other” line.

3.) As the previous picture shows, I have 5 disk partitions: vol0, vol1, …, vol4. Now mount either partition (vol4 for instance) to /mnt via command:

sudo mount vbox_sysdis/vol4 /mnt

Finally go to /mnt directory and there you are.

Unmount:

To un-mount the guest os file system, run command:

sudo umount /mnt

To un-mount the VBox disk image, run command:

umount ~/vbox_sysdisk

And you may finally remove that folder either from file manager or by running command in terminal:

rm -r ~/vbox_sysdisk

Running Ubuntu as virtual machine via VirtualBox? You may encounter permission issue to access the shared folder between host and guest.

Shared Folders is an useful feature for file sync between Virtualbox host and guest OSes. However, after you created one, the shared folder is marked with cross and lock icons. And it pops up an error dialog when you trying to open it:

Unhandled error message:
GDBus.Error:org.freedesktop.PolicyKit1.Error.Failed: Unix process subject does not have uid set.

Or it prompts permission issue while accessing from the left pane in file manager:

You do not have permissions necessary to view the contents of “xxx”

Fix shared folder permission issue:

The shared folder belongs to vboxsf group in the guest. All you need to do is add your user into this group.

There are a few ways to add an user to a group. Here I’m going to do it via a single command:

1. Firstly, start the virtual machine and login.
2. Open a terminal window from system app launcher.
3. When terminal opens, run command to check your username in case you don’t remember:

   whoami

4. Finally add user to vboxsf group (replace USER_NAME with what printed in last command.):

   sudo adduser USER_NAME vboxsf

Restart VM to apply change and enjoy!