Error installing Guest Additions

[rdh61]

Hi,

Host: Windows 10
Guest: Lubuntu 16.04

Problem: Cannot install Guest Additions. In my guest OS, under Devices, I do not have the option "Install guest additions", but only "Insert guest additions CD image..."
When I click there, I get the following error message:

"Unable to insert the virtual optical disk C:\Program Files\Oracle\Virtual Box\VBoxGuestAdditions.iso into the machine Lubuntu 16.04 LTS

Could not mount the media/drive 'C:\Program Files\Oracle\VirtualBox\VBoxGuestAdditions.iso' (VERR_PDM_MEDIA_LOCKED).

Result Code:
E_FAIL (0x80004005)
Component:
ConsoleWrap
Interface:
IConsole {872da645-4a9b-1727-bee2-5585105b9eed}
Callee:
IMachine {85cd948e-a71f-4289-281e-0ca7ad48cd89}"

Can somebody please help me to resolve this?

Many thanks.

[andyp73]

At a guess you either haven't ejected the Lubuntu install iso from the virtual optical drive or the guest additions ISO is already loaded to a different VM.

It is like physical optical drives, you can't put two disks into a single drive at the same time and you can't put the same disk into two different drives at the same time.

-Andy.

[rdh61]

So, not wishing to bother people here further by asking, "How can I verify and correct that?", I determined to find out by myself, and now I have a virtual machine which won't boot. Misunderstanding your suggestion, I went to "Virtual Media Manager", saw my "Lubuntu from ISO.vdi" and clicked "Release". I now realise why that was a mistake, but I do not know what to do now. Please help. Thank you.

[andyp73]

If you go to the storage tab of the guest settings you should be able to add a new disk to the IDE or SATA controller (depending which you have configured) and when prompted, select "existing disk". You should then be able to navigate to, and select, the pre-existing .vdi file.

-Andy.

[rdh61]

Thank you.