Reset admin password
There is one default admin user in any Umbraco installation. This is the first user of the system.
The first step is to clear the connection string to the database in the configuration. This is done to trigger the installation wizard.
That means that in your appsettings configuration files it should look like this:
Note that configuration can be read from many sources
Remember to check this connection string is not provided through environment variables or other configuration sources.
If you now open your browser and surf to the website, you will see that the installer launches. Enter your new details, and use the original connection string. You are good to go.
Make sure you protect a production websites from being highjacked as anyone will be able to reset the password during the last step. This does also work if your site is in an upgrading state.