as noted below  i think you need to assert what you support here  right now  if a user does rescue on an instance booted from volume  it looks to me like the following will happen root vhd path will return a non existent path self  vmutils detach vm disk will silently do nothing new disk with invalid path with be added this definitely will not work as the user intends  as it is unsupported at the moment that is fine  but it would be much nicer to the user to tell them that with a clear error message rather than leaving them wondering why their rescued instance does not work  also  i have not looked at the interaction with unrescue  but it is critical that the above mess can be unwound with unrescue  if it currently work it is presumably just luck tl dr not supporting everything is fine  but i think you need to explicitly check that root vhd path exists and there is only disk  if not  you need to error out early this might be generally bad  seems like the sort of thing you would want to know if it did not work  separate issue  though i do not know if this will explode or not 