Add option to skip VM driver PreCreateCheck

[thewilli]

Environment: Windows 10 Version 10.0.16299.904
Minikube: v0.34.1

The supported drivers provide a PreCreateCheck() method that is invoked by minikube in order to ensure the driver works properly and its prerequisites are fulfiled.
Unfortunately those prerequisites are not without flaws. The one implemented in the hyperv driver invokes some PowerShell as part of its checks. The one listed before checks if the user is part of the Hyper-V Administrators group. While this check is a good idea, it does not work if the computer joined a domain and cannot reach its Domain Controller. Therefore, when e.g. working in Home Office or in the train without network connectivity at all, I cannot use minikube in this setup.

Please add an option to skip (or ignore failing) PreCreateChecks.

The minishift project is doing something similar specific to hyperv, but I'd propose to just add a general I-know-what-I'm-doing-option to continue when those checks failed.

[tstromberg]

This sounds like a great idea, and I would be happy to review any PR that implements it.

[thewilli]

This sounds like a great idea, and I would be happy to review any PR that implements it.

@tstromberg okay, I'm on it. One question, though: I added a new configuration parameter to Cobra. This parameter, ignore-vm-driver-precheck (pretty long but self-explanatory) need to be accessed here (package k8s.io/minikube/pkg/minikube/machine). I have to use Viper in order to access the configuration parameter to not break the existing interfaces - there's no access to the corresponding config objects there.

My approach works, but I can't define the configurational key (i.e. flag name) next to the others. This would lead to circular imports.

Is there any other location to put this constant, or do you have another idea on how to solve this?

[tstromberg]

Flags should only be referenced in the main package, so I think we'll need to pass it into Create somehow. I agree that it isn't very straightforward: I can't think of a way to do this without modifying libmachine to accept a new value in the Host struct, or adding a specific flag to the hyperv driver.

Here is an example of the latter approach: #3734

To mimic this particular case, we would need to modify the upstream hyperv driver we use:
https://github.com/machine-drivers/machine/blob/master/drivers/hyperv/hyperv.go

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[priyawadhwa]

@thewilli are you still interested in implementing this issue?

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