Cry about...
Windows Hyper-V-Server

Logon failure: unknown username or bad password when trying to join hyper-v-server to a domain

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Symptom:

When attempting to join a domain using sconfig an error box is shown saying:

Domain

Logon failure: unknown username or password.

Possible Solutions:

1. Check that the domain name you are entering is the fully qualified domain name.
2. Check that you are entering a valid username and the correct password.
3. Instead of using sconfig, use powershell to add the hyper-v-server to the domain:

   The powershell cmdlet is Add-Computer:

   add-computer fully-qualified-domain-name

   for example:

   C:\> powershell

   Windows PowerShell

   Copyright (C) 2013 Microsoft Corporation. All rights reserved.

    

   PS C:\> add-computer mydomain.local

   It will then pop up a login box asking for the username and password with an account with rights to add to the domain. Done.

   Whilst you can specify the account to use on the command line if you wish (add -cred account-name) you cannot specify the password on the command line - it will always pop up a login box.

I never did resolve why this failed for me, but fortunately the powershell solution worked a treat.