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After I moved an ISO file to a new location, VirtualBox threw the above warning whenever I started the VirtualBox Manager. Moving the ISO file to its original location made the message go away; however, I was quite determined that the new location was the better choice. Convincing VirtualBox about this was harder than expected.
VirtualBox Warning - One or more virtual hard disks, CD/DVD or floppy disk image files are not currently accessible.
First of all, you can, of course, get rid of the prompt by checking Do not show this message again. However, these warnings sometimes point to a real problem and it therefore makes sense to click the Check button.
This will open the Virtual Media Manager, which you can also access through the VirtualBox File menu. The tab with the exclamation mark contains information about the missing file. In my case, it was a Windows 10 ISO file.
Missing file in Virtual Media Manager
You’ll see the file name and the original location. If you restore the file, the warning will disappear. If you deleted the file or want to move the file to a new location, things can get tricky. As you can see in the screenshot, all options to manage the ISO file are grayed out. Thus, I can’t tell Virtual Media Manager the new location of the file or that the file is no longer required.
You can see the reason in the Attached to field of the screenshot above. The ISO file is attached to a virtual machine, and VirtualBox therefore disapproves meddling with the file. The first solution that comes to mind is to simply remove the disk from the virtual drive.
Remove disk from virtual drive
In many cases, this will work. In my case, it didn’t. A closer look at the attached information reveals that the ISO file is not just attached to a virtual machine but also to a snapshot. The question is, how can you detach a virtual drive from a snapshot? I am unaware of any method that allows you to do this directly in the snapshot. One way to get rid of the problem is to simply delete the snapshot. You can do this in VirtualBox console by clicking the Snapshot tab of the virtual machine.
In my case, the snapshot belonged to a linked clone. Deleting the linked clone or removing the virtual drive in the corresponding VM doesn’t solve the problem; I also had to delete the snapshot. If you want to keep the VM that belongs to the snapshot, you first have to create a full clone of the snapshot and then delete the snapshot. Don’t forget to remove the virtual DVD from the new VM. Otherwise, the VirtualBox warning will show up again.