Raspberry Pi Desktop, Guest Additions: Access denied under root

Question

I've been trying to install Guest Additions for Raspbian Desktop on VirtualBox hosted on Linux. The script won't run even under root. How is it possible?

Answer 1

8. of the preferred answer here. Not much of an explanation, yet it certainly works.

# sh /media/cdrom0/VBoxLinuxAdditions.run

Answer 2

In my case this worked for me.

$ sudo apt update

$ sudo apt install build-essential module-assistant dkms

$ sudo m-a prepare

then select the menu devices/insert guest...

CD is mounted and select ok

$ sudo sh /media/cdrom/VBoxLinuxAdditions.run

$ sudo reboot

proudly borrowed from, https://www.neontribe.co.uk/debian-virtualbox-guest-additions/

I don't know why root wouldn't work for me sudo -i was enough