It should be possible to boot a guest with an unconnected hotplug disk

[dlippold]

If there is a hotplug virtual disk (a VDI file on an external drive) attached to a SATA controller, the virtual disk is unplugged in the running guest, the external drive is removed and the guest is shutdown, then the guest cannot be booted anymore. I got the following message:

Could not open the medium 'E:\VirtualBoxDisks\Lubuntu-16.04-Backup.vdi'.
VD: error VERR_PATH_NOT_FOUND opening image file 'E:\VirtualBoxDisks\Lubuntu-16.04-Backup.vdi' (VERR_PATH_NOT_FOUND).

Fehlercode:
E_FAIL (0x80004005)
Komponente:
MediumWrap
Interface:
IMedium {4afe423b-43e0-e9d0-82e8-ceb307940dda}

Steps to reproduce the problem:

1. Assume you have a Windows 7 host (other host may have the same problem), an USB drive (an USB stick may have the same problem) and a Linux guest (other guests may have the same problem).
2. Shut down the guest.
3. Connect the USB drive to the host.
4. Add a new virtual disk to the guest as a VDI file on the USB drive with a virtual SATA controller. Mark the virtual disk as hotpluggable.
5. Start the guest.
6. Check that the hotplug disk is there: ls /dev/sdb1
7. Unplug the disk: echo 1 > /sys/block/sdb/device/delete
8. Check that the hotplug disk is unplugged (output should be an error message): ls /dev/sdb1
9. Disconnect the USB drive from the host.
10. Shut down the guest.
11. Start the guest.

For a simple test you can omit the steps 5 to 8 and 10.

From my point of view a hotplug disk should be handed like a DVD: It is not necessary that it there (is in the drive) to boot the guest.

Workaround: Disconnect the hotplug disk by hand from the SATA controller before booting, in cold state between step 10 and 11 (in the GUI or by the command VBoxManage storagectl).

[Socratis]

I believe you have an over-complicated description. Steps 1-11 can be summarized as follows:

You cannot start the VM if a VDI is missing, even if the VDI is set as hotpluggable.

This pretty much describes your problem, right?. Because you would get the exact same behavior under the following conditions:

• The VDI was or wasn't hotplugable.
• The VDI was or wasn't residing in a USB drive.
• And BTW, this is independent of host or guest.

When you add/remove a VDI, you modify the .vbox file, the VM "recipe". What you're asking for is to be able to start the VM even if a VDI from the recipe is physically missing.

As you were told, and you also said in the forums, the situation can be changed at run-time with the "VBoxManage storageattach" command.

Please don't answer here, but in the related discussion in the forums: ​https://forums.virtualbox.org/viewtopic.php?f=6&t=86421. That's what "forums" means after all; a public place for discussion... :)