After upgrading VirtualBox on your system it is highly recommended to also update VirtualBox Guest Addons for your guest systems.
This should work automatically but typically doesn’t, at least in my case; just happened to me again after upgrading to VirtualBox 5.2.8.
How to update VirtualBox Guest Addons is described here:
In the “Devices” menu in the virtual machine’s menu bar, VirtualBox has a handy menu item named “Insert Guest Additions CD image”, which mounts the Guest Additions ISO file inside your virtual machine.
This did not work in my case: when clicking “Insert Guest Additions CD image” I get an error message which is not very specifc, it just says the desired CD image could not be mounted. A closer looks reveals that actually that image is mounted already, it just did not start automatically to perform the update.
Here is what I do in this case:
- Open a termin window
- Type ‘df -h’ to find the path to my mounted CD image. In my case that entry looks like this:
/dev/sr0 56M 56M 0 100% /media/amagard/VBox_GAs_5.2.8
- cd to this path ( here: /media/amagard/VBox_GAs_5.2.8 )
- Type ‘sudo ./autorun.sh’
This actually kicked off the installation of the VirtualBox Guest Addons.