# VirtualBox unbind

With the **VirtualBox unbind** trigger, the workflow process starts when the virtual box is unbound from a file. A [Virtual Box](/data-mover-1.21/contracts/virtual-boxes.md) is a way to classify and tag files in Data Mover. 

For example, when a workflow template removes the Virtual Box from a file, an event is emitted and contracts having the **VirtualBox Unbind** trigger on that virtual box will start. 

The removal of a Virtual Box from a file is executed with the [Unbind VirtualBox](/data-mover-1.21/workflow-templates/service-tasks/triggerable-service-tasks.md#unbind-virtualbox) service task.

The **VirtualBox unbind** trigger requires a virtual box.

**Execution Variable**

When executed, this trigger adds an execution variable named `file`, of type `FileDetail`. Its attributes are set based on the information sent from the event that initiated the trigger. 


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