Missing guide: How to try Windows MDM (`fleetctl preview`)

[forderud]

Fleet version: N/A for this missing guide bug

Web browser and operating system: N/A for this missing guide bug

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💥  Actual behavior

• @forderud: Using fleetctl preview, I've now attempted to activate Windows MDM as instructed, but am then experiencing the following error:
  "Couldn't turn on Windows MDM. Please configure Fleet with a certificate and key pair first. Learn more"

🛠️ To fix

Add a "fleetctl preview" section to the Windows MDM setup guide.

This section includes instructions on how to turn on Windows MDM when using fleetctl preview.

Product designer: @noahtalerman

🧑‍💻  Steps to reproduce

• @forderud: I've tried to update %USERPROFILE%\.fleet\preview\docker-compose.yml the following two ways:

1. Add fleet-mdm-win-wstep.crt and fleet-mdm-win-wstep.key to the the %USERPROFILE%\.fleet\preview folder, and add the following to docker-compose.yml:

services:
  # Normal Fleet server running TLS with a self-signed cert to handle the osquery connections.
  fleet01:
    environment:
      FLEET_MDM_WINDOWS_WSTEP_IDENTITY_CERT: fleet-mdm-win-wstep.crt
      FLEET_MDM_WINDOWS_WSTEP_IDENTITY_KEY: fleet-mdm-win-wstep.key

2. Add the following to docker-compose.yml:

services:
  # Normal Fleet server running TLS with a self-signed cert to handle the osquery connections.
  fleet01:
    environment:
      FLEET_MDM_WINDOWS_WSTEP_IDENTITY_CERT_BYTES: |
        -----BEGIN CERTIFICATE-----
        ...
        -----END CERTIFICATE-----
      FLEET_MDM_WINDOWS_WSTEP_IDENTITY_KEY_BYTES: |
        -----BEGIN RSA PRIVATE KEY-----
        ...
        -----END RSA PRIVATE KEY-----

🕯️ More info (optional)

• @forderud: The Windows MDM setup documents that the Fleet needs to be configured with a certificate and key file in the FLEET_MDM_WINDOWS_WSTEP_IDENTITY_CERT_BYTES and FLEET_MDM_WINDOWS_WSTEP_IDENTITY_KEY_BYTES environment variables. However, it is unclear to me how to set these variables when attempting to run a preview version of Fleet locally from a Windows-based host.

It's been claimed in #29576 that these variables are passed through Docker in the docker-compose.yml file. However, I'm struggling to understand precisely how to do so, so it would be highly appreciated if the documentation could be extended to better explain the process for a newbie like me.

[georgekarrv]

Thanks for filing this, we will get to it shortly!