// setupContainerSupport determines what containers can be run on this machine and
// initialises suitable infrastructure to support such containers.
func (a *MachineAgent) setupContainerSupport(runner worker.Runner, st *api.State, entity *apiagent.Entity, agentConfig agent.Config) error {
	var supportedContainers []instance.ContainerType
	// We don't yet support nested lxc containers but anything else can run an LXC container.
	if entity.ContainerType() != instance.LXC {
		supportedContainers = append(supportedContainers, instance.LXC)
	}
	supportsKvm, err := kvm.IsKVMSupported()
	if err != nil {
		logger.Warningf("determining kvm support: %v\nno kvm containers possible", err)
	}
	if err == nil && supportsKvm {
		supportedContainers = append(supportedContainers, instance.KVM)
	}
	return a.updateSupportedContainers(runner, st, entity.Tag(), supportedContainers, agentConfig)
}

func setAgentPassword(newPw, oldPw string, a agent.Agent, entity *apiagent.Entity) error {
	// Change the configuration *before* setting the entity
	// password, so that we avoid the possibility that
	// we might successfully change the entity's
	// password but fail to write the configuration,
	// thus locking us out completely.
	if err := a.ChangeConfig(func(c agent.ConfigSetter) error {
		c.SetPassword(newPw)
		c.SetOldPassword(oldPw)
		return nil
	}); err != nil {
		return err
	}
	return entity.SetPassword(newPw)
}