Docker-Docs/machine/DRIVER_SPEC.md

description	keywords	published	title
machine	machine, orchestration, install, installation, docker, documentation	false	Machine driver specification v1

This is the standard configuration and specification for version 1 drivers.

Along with defining how a driver should provision instances, the standard also discusses behavior and operations Machine expects.

Requirements

The following are required for a driver to be included as a supported driver for Docker Machine.

Base Operating System

The provider must offer a base operating system supported by the Docker Engine.

Currently Machine requires Ubuntu for non-Boot2Docker machines.

API Access

We prefer accessing the provider service via HTTP APIs and strongly recommend using those over external executables. For example, using the Amazon EC2 API instead of the EC2 command line tools. If in doubt, contact a project maintainer.

SSH

The provider must offer SSH access to control the instance. This does not have to be public, but must offer it as Machine relies on SSH for system level maintenance.

Provider Operations

The following instance operations should be supported by the provider.

Create

Create launches a new instance and make sure it is ready for provisioning. This includes setting up the instance with the proper SSH keys and making sure SSH is available including any access control (firewall). This should return an error on failure.

Remove

Remove removes the instance from the provider. This should remove the instance and any associated services or artifacts that were created as part of the instance including keys and access groups. This should return an error on failure.

Start

Start starts a stopped instance. This should ensure the instance is ready for operations such as SSH and Docker. This should return an error on failure.

Stop

Stop stops a running instance. This should ensure the instance is stopped and return an error on failure.

Kill

Kill forcibly stops a running instance. This should ensure the instance is stopped and return an error on failure.

Restart

Restart restarts a running instance. This should ensure the instance is ready for operations such as SSH and Docker. This should return an error on failure.

Status

Status returns the state of the instance. This should return the current state of the instance (running, stopped, error, etc). This should return an error on failure.

Testing

Testing is strongly recommended for drivers. Unit tests are preferred as well as inclusion into the integration tests.

Maintaining

Driver plugin maintainers are encouraged to host their own repo and distribute the driver plugins as executables.

Implementation

The following describes what is needed to create a Machine Driver. The driver interface has methods that must be implemented for all drivers. These include operations such as Create, Remove, Start, Stop etc.

For details see the Driver Interface.

To provide this functionality, you should embed the drivers.BaseDriver struct, similar to the following:

type Driver struct {
    *drivers.BaseDriver
    DriverSpecificField string
}

Each driver must then use an init func to "register" the driver:

func init() {
    drivers.Register("drivername", &drivers.RegisteredDriver{
        New:            NewDriver,
        GetCreateFlags: GetCreateFlags,
    })
}

Flags

Driver flags are used for provider specific customizations. To add flags, use a GetCreateFlags func. For example:

func GetCreateFlags() []cli.Flag {
    return []cli.Flag{
        cli.StringFlag{
            EnvVar: "DRIVERNAME_TOKEN",
            Name:   "drivername-token",
            Usage:  "Provider access token",

        },
        cli.StringFlag{
            EnvVar: "DRIVERNAME_IMAGE",
            Name:   "drivername-image",
            Usage:  "Provider Image",
            Value:  "ubuntu-14-04-x64",
        },
    }
}

Examples

You can reference the existing Drivers as well.