I followed the guide here at https://shovik.com/blog/8-deploying-phoenix-apps-with-docker and it was advised to not bundle the erts files, that is, set include_erts: false in the rel/config.exs. I was both able to run mix docker.build and mix docker.release but when it comes time to running the container it errors out stating

{"init terminating in do_boot",{load_failed,[file_io_server,heart,lists,error_handler,erl_eval,code_server,erl_lint,application_master,gen_server,kernel,file_server,application,filename,gen_event,gen,supervisor,code,ets,erl_parse,proc_lib,file,application_controller,error_logger]}}
init terminating in do_boot ()

Crash dump is being written to: erl_crash.dump...done

Shutting down..
Node is not running!

If I then instead set to include erts to true
set include_erts: true

then it is able to run the container/initiate the phoenix server. If it helps at all I'm running this on OSX without any other changes to the standard included Dockerfile build and release files.