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Drivers

site/content/en/docs/contrib/drivers.en.md

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This document is written for contributors who are familiar with minikube, who would like to add support for a new VM driver.

This document discusses how to modify minikube, so that this driver may be used by minikube start --driver=<new_driver>.

Builtin vs External Drivers

Most drivers are built-in: they are included into minikube as a code dependency, so no further installation is required. There are two primary cases you may want to use an external driver:

  • The driver has a code dependency which minikube should not rely on due to platform incompatibilities (kvm2) or licensing
  • The driver needs to run with elevated permissions (hyperkit)

External drivers are instantiated by executing a command docker-machine-driver-<name>, which begins an RPC server which minikube will talk to.

Integrating a driver

The integration process is effectively 3 steps.

  1. Create a driver shim within k8s.io/minikube/pkg/minikube/drivers
    • Add Go build tag for the supported operating systems
    • Define the driver metadata to register in DriverDef
  2. Add import in pkg/minikube/cluster/default_drivers.go so that the driver may be included by the minikube build process.

The driver shim

The primary duty of the driver shim is to register a VM driver with minikube, and translate minikube VM hardware configuration into a format that the driver understands.

Registering your driver

The docs on registry are available here: https://pkg.go.dev/k8s.io/minikube/pkg/minikube/registry

DriverDef is the main struct to define a driver metadata. Essentially, you need to define 4 things at most, which is pretty simple once you understand your driver well:

  • Name: unique name of the driver, it will be used as the unique ID in registry and as --driver option in minikube command

  • Builtin: true if the driver should be builtin to minikube (preferred). false otherwise.

  • ConfigCreator: how to translate a minikube config to driver config. The driver config will be persistent on your $USER/.minikube directory. Most likely the driver config is the driver itself.

  • DriverCreator: Only needed when driver is builtin, to instantiate the driver instance.

Any Questions: please ping your friend @anfernee or the #minikube Slack channel.