Error message while deleting snapshot

[systemdlete]

I was trying to clear out some old snapshots of a VM when I received a message. I did not save the message because I thought it was a momentary glitch. But when I tried to boot the VM, it failed, not even reaching grub. The VM appears to be irreparably damaged. Here is a complete history of events.

The VM consisted, originally, of 3 virtual disks (16GB,64GB,16GB), each having several snapshots, and has 4GB ram allocated to it. The host had ample disk space at that time (about 60GB). It is a Thuban Athlon II X6 CPU with 32 GB memory. There is one other VM running on the same host but it is using a very nominal amount of resources and is rarely updated.

While investigating a different bug, I had tried upgrading from v6.1.42 to v7.0.6. When that did not address the problem, I reverted back to v6.1.42 (and this may have been the problem all along, without my realizing it; various posts indicate this is not recommended, although in the past I had been instructed that it was safe).

Sometime later, I wanted to reconfigure my filesystems within the VM. I wanted to have plenty of disk space, and I saw that the 3rd of 3 virtual disks was not even being used, so I decided to detach it from the VM and delete it to recover disk space. However, before actually deleting the VDI file for that 3rd disk, I decided to boot the VM just to make sure it still worked, and it did. Satisfied with that, I proceeded to remove snapshots from the VM (I had still not quite deleted the VDI yet because there were snapshots preventing that).

The very first snapshot I removed was proceeding for some time when, suddenly, an error message appeared. I did not note the specific message (and, yes, I should have!) because I figured this was just a momentary glitch (I was wrong, apparently). So I ignored it. I wanted to try again, but that snapshot was gone. Recall that this was happening while the 3rd VDI was detached from the VM.

I tried to re-launch the VM, but it failed, not even reaching the grub menu. So I tried re-attaching the 3rd VDI, but even with it attached again, the VM would not boot. BTW, these failures result in Aborted state of the VM.

Researching the issue further, I note that there are a total of 10 snapshots listed in the media manager for the 3 virtual disks originally attached to the VM. However, only 9 vdi files exist in the Snapshots folder, the missing one being the VDI that the log believes is missing. Interestingly, the missing snapshot vdi is associated with the 1st, not the 3rd, virtual disk of the VM.

This is a Linux host and a Linux guest. Devuan Chimaera with all the latest patches and updates, running vbox 6.1.42 (except for that momentary roll-forward/rollback I mentioned, above).

If removing one or more virtual disks from a VM, or removing one or more snapshots from a VM, or a combination of these, is likely to cause a consistency or integrity issue for the VM, VirtualBox should issue a warning. Better yet, it should not permit it, period. I know there are a myriad of different possibilities, but a user should not be enticed into using the GUI (and the command line tools as well, to some extent) to perform operations which could result in permanent damage to the VM.

I realize that this might be a complex bit of logic, but it really is badly needed. The error message (which I did not record) should probably be logged somewhere, along with other error messages, by vbox itself. For one thing, I note that *some* of these messages cannot be simply copied from the desktop for some reason or another. Best vbox logs these items internally, I think.

I posted the issue at ​https://forums.virtualbox.org/viewtopic.php?f=7&t=108658, which you may view for more details.

I am posting this as an enhancement request, because perhaps some users might want the flexibility of being allowed to make changes that could result in damage at their own risk. As a relatively lightweight user of virtualbox, I don't want to assume everyone wants this same level of safety. If you feel it is a bug, please feel free to change it.

[systemdlete]

Log from attempted boot of damaged VM

[systemdlete]

Media Manager view of affected virtual disks