#Here are the manual steps to install VirtualBox Guest Additions kernel modules inside the VM:

#Download the ISO file, e.g.

wget http://download.virtualbox.org/virtualbox/7.0.4/VBoxGuestAdditions_7.0.4.iso -P /tmp 

#Mount the ISO file:

sudo mount -o loop /tmp/VBoxGuestAdditions_7.0.4.iso /mnt

#Run installer (add -x after sh to debug):

sudo sh /mnt/VBoxLinuxAdditions.run

#To find the right version of ISO file, check it at: http://download.virtualbox.org/virtualbox/