rebar/test/upgrade_project

Building version 0.1

rebar compile
rebar generate
mv rel/dummy rel/dummy_0.1
rebar clean
# start the release:
cd rel/dummy_0.1
bin/dummy console

erl> dummy_server:get_state().
erl> dummy_server:set_state(123).
erl> dummy_server:get_state().

Building version 0.2

# Now, in another terminal we prepare an upgrade..

# change release version numbers from 0.1 to 0.2 in
$EDITOR apps/dummy/src/dummy.app.src
$EDITOR rel/reltool.config

rebar compile
rebar generate
# previous_release path is relative to your rel directory
rebar generate-appups previous_release=dummy_0.1
rebar generate-upgrade previous_release=dummy_0.1
tar -zvtf rel/dummy_0.2.tar.gz

Deploying with release_handler

mv rel/dummy_0.2.tar.gz rel/dummy_0.1/releases/

# Now use release_handler in the running erlang console for the deploy:

erl> release_handler:unpack_release("dummy_0.2").
erl> release_handler:install_release("0.2").
erl> release_handler:make_permanent("0.2").

erl> release_handler:which_releases().
erl> dummy_server:get_state().