Last night I was trying to get shared folders working using VirtualBox. I have the host as Ubuntu 12.04 and a guest using Ubuntu 11.04. For the life of me I couldn’t get them to work. I followed the instructions on installing the Linux Guest Additions from VirtualBox’s site and set up shared folders the same way many tutorials/blogs suggested, but every time I went to mount the shared folder I would get this error:

/sbin/mount.vboxsf: mounting failed with the error: No such Device

I finally found a post explaining that the issue was the installation of modules while installing the Guest Additions. VirtualBox’s website instructs to install just dkms before running the Guest Additions script, but this was incorrect. One indication that this is the issue is to run ls mod | grep vbox. You shouldn’t see vboxsf.

In order to build the modules necessary for shared folders, the following three packages need to be installed before running the Guest Additions installation script:

sudo apt-get install dkms build-essential linux-headers-generic      

After that, I re-ran the Guest Additions script by connecting the VBoxGuestAdditions.iso as a storage device (using phpvirtualbox), mounting the device at /dev/scd0, and running the script:

sudo mount /dev/scd0 /media/cdrom
cd /media/cdrom
./VBoxLinuxAdditions.run

Once that had completed, I restarted and ran ls mod | grep vbox. You should see see vboxsf.

One that’s done, you should be able to mount your shared folders, like so:

mount -t vboxsf -o uid=1000,gid=1000 d /media/sf_d

I put one of those commands for each of my shared folders in /etc/rc.local. Make sure you create the sf_d folder in /media before trying to mount it there, and change uid and gid to the user you want the mount to be mounted under.