Problem scenario: You are trying to install Guest Additions on a Linux server. You mount the CD/DVD/.iso through Oracle VirtualBox to /media/VirtualBoxGuestAdditions. On the host virtual server the /media/VirtualBoxGuestAdditions (the directory where the CD/DVD/.iso was mounted) has no files. You try to unmount the device and remount the device. But you see no files. You are unable to run "./VBoxLinuxAdditions.run" because the file is not where it should be. What do you do to solve this problem?
Reboot the Linux server. Mount the device again (e.g., with a command like this "mount /dev/cdrom /media/VirtualBoxGuestAdditions").