110 lines
4.3 KiB
Markdown
110 lines
4.3 KiB
Markdown
---
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title: "Drivers"
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date: 2019-07-31
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weight: 4
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description: >
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How to create a new VM Driver
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---
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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.
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minikube relies on docker-machine drivers to manage machines. This document discusses how to modify minikube, so that this driver may be used by `minikube start --driver=<new_driver>`.
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## Creating a new driver
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See https://github.com/machine-drivers, the fork where all new docker-machine drivers are located.
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## Builtin vs External Drivers
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Most drivers are built-in: they are included into minikube as a code dependency, so no further
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installation is required. There are two primary cases you may want to use an external driver:
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- The driver has a code dependency which minikube should not rely on due to platform incompatibilities (kvm2) or licensing
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- The driver needs to run with elevated permissions (hyperkit)
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External drivers are instantiated by executing a command `docker-machine-driver-<name>`, which begins an RPC server which minikube will talk to.
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### Integrating a driver
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The integration process is effectively 3 steps.
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1. Create a driver shim within `k8s.io/minikube/pkg/minikube/drivers`
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- Add Go build tag for the supported operating systems
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- Define the driver metadata to register in `DriverDef`
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2. Add import in `pkg/minikube/cluster/default_drivers.go` so that the driver may be included by the minikube build process.
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### The driver shim
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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.
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### Registering your driver
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The godoc of registry is available here: <https://godoc.org/k8s.io/minikube/pkg/minikube/registry>
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[DriverDef](https://godoc.org/k8s.io/minikube/pkg/minikube/registry#DriverDef) is the main
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struct to define a driver metadata. Essentially, you need to define 4 things at most, which is
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pretty simple once you understand your driver well:
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- Name: unique name of the driver, it will be used as the unique ID in registry and as
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`--driver` option in minikube command
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- Builtin: `true` if the driver should be builtin to minikube (preferred). `false` otherwise.
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- ConfigCreator: how to translate a minikube config to driver config. The driver config will be persistent
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on your `$USER/.minikube` directory. Most likely the driver config is the driver itself.
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- DriverCreator: Only needed when driver is builtin, to instantiate the driver instance.
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## Integration example: vmwarefusion
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All drivers are located in `k8s.io/minikube/pkg/minikube/drivers`. Take `vmwarefusion` as an example:
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```golang
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// +build darwin
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package vmwarefusion
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import (
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"github.com/docker/machine/drivers/vmwarefusion"
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"github.com/docker/machine/libmachine/drivers"
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cfg "k8s.io/minikube/pkg/minikube/config"
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"k8s.io/minikube/pkg/minikube/constants"
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"k8s.io/minikube/pkg/minikube/localpath"
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"k8s.io/minikube/pkg/minikube/registry"
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)
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func init() {
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registry.Register(registry.DriverDef{
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Name: "vmwarefusion",
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Builtin: true,
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ConfigCreator: createVMwareFusionHost,
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DriverCreator: func() drivers.Driver {
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return vmwarefusion.NewDriver("", "")
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},
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})
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}
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func createVMwareFusionHost(config cfg.ClusterConfig) interface{} {
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d := vmwarefusion.NewDriver(config.Name, localpath.MiniPath()).(*vmwarefusion.Driver)
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d.Boot2DockerURL = download.LocalISOResource(config.MinikubeISO)
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d.Memory = config.Memory
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d.CPU = config.CPUs
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d.DiskSize = config.DiskSize
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d.SSHPort = 22
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d.ISO = d.ResolveStorePath("boot2docker.iso")
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return d
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}
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```
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- Within the `init()` function, register a `DriverDef` in registry. Specify the metadata in the `DriverDef`. As mentioned
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earlier, it's builtin, so you also need to specify `DriverCreator` to tell minikube how to create a `drivers.Driver`.
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- Another important thing is `vmwarefusion` only runs on MacOS. You need to add a build tag on top so it only
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runs on MacOS, so that the releases on Windows and Linux won't have this driver in registry.
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- Last but not least, import the driver in `pkg/minikube/cluster/default_drivers.go` to include it in build.
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Any Questions: please ping your friend [@anfernee](https://github.com/anfernee) or the #minikube Slack channel.
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