vditool refuses to write to block devices

[branen salmon]

vditool fails with VERR_ALREADY_EXISTS when trying to write to a raw block device (e.g. /dev/sda). This means that one must create a temporary file to unpack a VDI onto a physical drive, which can be a very expensive proposition. vditool should either recognize a block device and write without complaint or should provide a command line argument to suppress VERR_ALREADY_EXISTS.

[Frank Mehnert]

Please reopen this bug if still relevant. Please don't use vditool. The required function should be available in VBoxManage.