Unable to mount the CD/DVD image on VirtualBox

Solution 1:

The error you get is likely because the Guest Additions CD image is already mounted.

To see all mounted drives open a terminal in the guest to issue mount. This will give you (among others) a line similar to this:

/dev/sr0 on /media/takkat/VBOXADDITIONS_4.2.12_849801 type iso9660 (ro,nosuid,nodev,uid=1000,gid=1000,iocharset=utf8,mode=0400,dmode=0500,uhelper=udisks2)

In the Unity Launcher you will see a CD-ROM icon. To unmount the CD right click on this icon and select "Eject".

We can not unmount the Guest Additions CD from the command line when mounted with the help of then Virtual Box Manager. Please select "Devices -> CD/DVD Devices -> Remove disk from virtual drive" and choose "Force unmount" to remove the CD iso.

To install guest additions we will have to load the CD again from Virtual Box Manager and select the Icon from the Unity Launcher.

See also the following questions which also has a command line method for installing guest additions:

• How do I install Guest Additions in a VirtualBox VM?

Solution 2:

I tried this and it worked:

1. From the terminal (Ctrl+Alt+T) and enter the following commands:

   cd /mnt
   cd /cdrom
   eject
   

2. From the VirtualBox menu (top left pane) go to "device" and insert guest additions (it should work this time)

3. Then from the terminal again type:

   sudo sh /media/cdrom/VBoxLinuxAdditions.run