Driver

What is a Driver

For a higher level overview of drivers from a user viewpoint, see drivers.

The koble package uses a Driver (defined by package pkg/driver) interface to control and manage virtual machines and networks. The Driver Godoc reference shows the functions that must be defined for a type to satisfy the interface. This means that we can have multiple implementations, and therefore different virtualisation technologies, without having to change any code in pkg/koble.

There are currently two implementations of the Driver interface:

podman (pkg/driver/podman)
uml (pkg/driver/uml)

These provide driver types which have the correct methods to satisfy the interface defined by pkg/driver.

Table 1. Key interfaces and implementations
Interface (pkg/driver)	Podman Implementation	UML Implementation
Driver	PodmanDriver	UMLDriver
Machine	Podman Machine	UML Machine
Network	Podman Network	UML Network

Developing a New Driver

The easiest way to create a driver is to look at the Godoc references for the interfaces and create types to satisfy these. Looking at the implementations of the other drivers (particularly in pkg/driver/podman) is likely to help understand how to write driver functions.

To make a driver package available to the koble binary, it needs to be registered in cmd/kob/driver.go:

func init() {
	driver.RegisterDriver("podman", func() driver.Driver {
		return new(podman.PodmanDriver)
	})
	driver.RegisterDriver("uml", func() driver.Driver {
		return new(uml.UMLDriver)
	})
	// new addition
	driver.RegisterDriver("mynewdriver", func() driver.Driver {
		return new(mypkg.MYDriver)
	})
	// end of new addition
	err := driver.RegisterDriverCmds(driverCmd)

    ...
}