If you are setting up a secured NiFi instance for the first time, you must manually designate an "Initial Admin Identity" in the authorizers.xml file. This initial admin user is granted access to the UI and given the ability to create additional users, groups, and policies. The value of this property could be a DN (when using certificates or LDAP) or a Kerberos principal. If you are the NiFi administrator, add yourself as the "Initial Admin Identity".

Here is an example LDAP entry using the name John Smith:

<authorizer>
        <identifier>file-provider</identifier>
        <class>org.apache.nifi.authorization.FileAuthorizer</class>
        <property name="Authorizations File">./conf/authorizations.xml</property>
        <property name="Users File">./conf/users.xml</property>
        <property name="Initial Admin Identity">cn=John Smith,ou=people,dc=example,dc=com</property>
        <property name="Legacy Authorized Users File"></property>
        <!--
        <property name="Node Identity 1"></property>
        <property name="Node Identity 2"></property>
        -->
    </authorizer>
</authorizers>

Here is an example Kerberos entry using the name John Smith and realm NIFI.APACHE.ORG:

<authorizer>
        <identifier>file-provider</identifier>
        <class>org.apache.nifi.authorization.FileAuthorizer</class>
        <property name="Authorizations File">./conf/authorizations.xml</property>
        <property name="Users File">./conf/users.xml</property>
        <property name="Initial Admin Identity">johnsmith@NIFI.APACHE.ORG</property>
        <property name="Legacy Authorized Users File"></property>
        <!--
        <property name="Node Identity 1"></property>
        <property name="Node Identity 2"></property>
        -->
    </authorizer>
</authorizers>

After you have edited and saved the authorizers.xml file, restart NiFi. The "Initial Admin Identity" user and administrative policies are added to the users.xml and authorizations.xml files during restart. Once NiFi starts, the "Initial Admin Identity" user is able to access the UI and begin managing users, groups, and policies.

For a brand new secure flow, providing the "Initial Admin Identity" gives that user access to get into the UI and to manage users, groups and policies. But if that user wants to start modifying the flow, they need to grant themselves policies for the root process group. The system is unable to do this automatically because in a new flow the UUID of the root process group is not permanent until the flow.xml.gz is generated. If the NiFi instance is an upgrade from an existing flow.xml.gz or a 1.x instance going from unsecure to secure, then the "Initial Admin Identity" user is automatically given the privileges to modify the flow.