Stolen from etorrent :)

reltool.config example

{sys, [
       %%% This says where to look for applications
       {lib_dirs, ["../deps", "../apps"]},
       %%% Name and version of the release.
       %%% The list is the list of applications to include and start when the embedded system is booted
       {rel, "etorrent", "1.2.0",
        [
         kernel,
         stdlib,
	 crypto,
	 inets,
         sasl,
	 gproc,
	 etorrent,
	 riak_err
        ]},
       %%% Another release that is also included in the bundle, this time for dev work
       %%% Note how some applications are just loaded but not started.
       {rel, "etorrent_dev", "1.2.0",
        [
         kernel,
         stdlib,
	 crypto,
	 inets,
         sasl,
	 gproc,
	 {tv, load},
         gs,
	 {appmon, load},
	 etorrent,
	 riak_err
        ]},
       %%% A target for a minimal test start of the embedded system
       {rel, "start_clean", "",
        [
         kernel,
         stdlib
        ]},
       %%% Naming
       {boot_rel, "etorrent"},
       {profile, embedded},
       %%% The next sections define some rules for inclusion/exclusion of specific apps. Some of these are only
       %%% needed for R13B but they are included here to make us run on R13.
       {excl_sys_filters, ["^bin/.*",
                           "^erts.*/bin/(dialyzer|typer)"]},
       {app, sasl, [{incl_cond, include}]},
       {app, gproc, [{incl_cond, include}]},
       {app, riak_err, [{incl_cond, include}]},
       {app, etorrent, [{incl_cond, include}]}
      ]}.

%%% Where to drop the release (./etorrent really)
{target_dir, "etorrent"}.

%%% Where to merge configuration variables from
{overlay_vars, "vars.config"}.

%%% A list of rules creating needed directories and copying support files for the embedded system.
{overlay, [
           {mkdir, "log/sasl"},
	   {mkdir, "log/webui"},
           {copy, "files/erl", "{{erts_vsn}}/bin/erl"},
           {copy, "files/nodetool", "{{erts_vsn}}/bin/nodetool"},
           {copy, "files/etorrent", "bin/etorrent"},
           {template, "files/app.config", "etc/app.config"},
           {copy, "files/vm.args", "etc/vm.args"}
           ]}.