For more details, see About Splunk Free in the Splunk Enterprise Admin Manual. It says:
There is no authentication or user and role management when using Splunk Free. This means:
There is no login. The command line or browser can access and control all aspects of Splunk Free with no user and password prompt.
All accesses are treated as equivalent to the admin user. There is only one role (admin), and it is not configurable. You cannot add more roles or create user accounts.
Searches are run against all public indexes, 'index=*'.
Restrictions on search, such as user quotas, maximum per-search time ranges, and search filters, are not supported.
The capability system is disabled. All available capabilities are enabled for all users accessing Splunk Free.
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