mjhjmtu

I've been trying for hours to get Guest Additions running on Debian 9 in VirtualBox.
I'm not very much into Linux I'm a beginner. I tried to install Guest Additions via VirtualBox, via Direct download from virtualbox.org and via apt.
Everytime fail with Kernel headers. But I installed them as shown in several tutorials. (first I tried linux-headers-$(uname -r) later linux-headers-4.9.0-3-common)
The last thing I tried was working on Debian 8 where I had the same problem

apt-get install virtualbox-guest-dkms virtualbox-guest-x11 linux-headers-$(uname -r)

The additions seemed to be installed. I didn't get an error when I tried to add shared folders. Before I got a message everytime saying that the GuestAdditions are not installed.

But after reboot I still have no fullscreen 16:9 display and there are no shared folders mounted

What's the problem? What can I do to fix this problem?

This works for me on Stretch (Debian 9). If it doesn't work for you, you'll need to update your question with contrasting information:

1. 
   

   First ensure that contrib repository has been added to your sources.list. If the following command returns nothing you need to add it.

   
   
   

   grep -rq 'stretch/.* contrib' /etc/apt/sources.list,.d 2>/dev/null && echo ok
   

   
   
   

   Expected output

   
   
   

   ok
   

   
   


2. 
   

   Update the repository and install the necessary set of packages.

   
   
   

   apt-get update
   apt-get install build-essential module-assistant
   module-assistant prepare
   

   
   


3. 
   

   Mount and run the VirtualBox Guest Additions image. Ensure the DVD image is available by going to the Guest window and then using the menu Devices > Insert Guest Additions Image... If you get an error here that you cannot understand, report it back in your question.

   
   
   

   mount /media/cdrom
   bash /media/cdrom/VBoxLinuxAdditions.run
   

   
   
   

   Expected output

   
   
   

   mount: /dev/sr0 is write-protected, mounting read-only
   
   Verifying archive integrity... All good.
   Uncompressing VirtualBox 5.2.8 Guest Additions for Linux........
   VirtualBox Guest Additions installer
   ...
   

   
   


4. 
   

   Check that the modules have been loaded into the running kernel. You may need to reboot to see this take effect (but I didn't).

   
   
   

   lsmod | grep vb
   

   
   
   

   Expected output (ignore the column of high-valued numbers)

   
   
   

   vboxvideo 36864 1
   ttm 98304 1 vboxvideo
   drm_kms_helper 155648 1 vboxvideo
   drm 360448 4 vboxvideo,ttm,drm_kms_helper
   vboxsf 45056 0
   vboxguest 286720 1 vboxsf