After you have configured and used a VM, you may want to modify it over time by adding, upgrading, or deleting devices and software. In fact, you may even be testing the effects of these actions on the VM. You can change a VM in many ways, and normally you can effect the change on a VM easier and faster than on a physical machine.
While a VM is running you can only review the configuration file. To modify a configuration you must power off the VM. You can modify most settings for a VM but not all of them.
To modify a VM's configuration: