Install VB Extensions on Ubuntu 18.04

[jgossage]

I am using Ubuntu 18.04 desktop and have installed VirtualBox 6.1.4 without problems. However, when I attempt to install VirtualBox extensions 6.1.4, the program tries to authenticate to Ubuntu as a superuser and fails. The dialog box presented works properly in all other instances and attempts to use sudo in a terminal command line always work. It is not clear to me whether this is a VirtualBox problem or an Ubuntu problem. Could I please have some advice? The net result is that I am unable to install VirtualBox Extensions.

[scottgus1]

On Windows hosts it is necessary to run Virtualbox as Administrator to install the Extension Pack, since the EP goes in the Virtualbox installation folder, by default "C:\Program Files", which requires Admin privileges to write into. If Linux has a similar arrangement, you might need to open the main Virtualbox window via 'sudo', if such a thing is possible, whatever the Linux equivalent of Windows' "Run As Administrator".

Alternatively, the Extension Pack is an extension-renamed gzip file. With the main Virtualbox window and all guests or other Virtualbox processes closed, you can open the gzip, unzip the folder called "." into the Virtualbox installation folder's "ExtensionPacks" subfolder, then rename "." to "Oracle_VM_VirtualBox_Extension_Pack":

Gzip extractor, "." folder into {linux-install-path}/Virtualbox/ExtensionPacks
v
{linux-install-path}/Virtualbox/ExtensionPacks/. <- rename "."
v
{linux-install-path}/Virtualbox/ExtensionPacks/Oracle_VM_VirtualBox_Extension_Pack

Start the main Virtualbox window, and you'll have the EP installed.