In dnscontrol-Linux version: dnscontrol 0.1.0 (c52ff67386750e96138fe78f0631d757f928f452) built 14 Mar 17 00:32 UTC (current latest compiled release)

Everything in the utility (help text etc) defaults to creds.json, documentation indicates providers.json is default. https://github.com/StackExchange/dnscontrol/blob/master/docs/getting-started.md