Download an Erlang source file with an appropriate version and unwrap it:

tar -zxf otp_src_20.1.tar.gz						
cd otp_src_20.1

Export the working directory

export ERL_TOP=`pwd`					      

And run configure scripts:

sudo ./configure

If you notice a crash with certain locales try:

export LANG=C

Build Erlang:

sudo make

Optionally build and run tests:

make release_tests							    
cd release/tests/test_server						
$ERL_TOP/bin/erl -s ts install -s ts smoke_test batch -s init stop

Check if none fail at $ERL_TOP/release/tests/test_server/index.html.

Proceed to install Erlang:

cd $ERL_TOP
sudo make install

Export to $PATH, this is important. Full OTP is needed in PATH environment for Rebar!

export PATH=$ERL_TOP/bin:$PATH

Clone from git:

git clone https://github.com/erlang/rebar3			
cd rebar3/
export REBAR3_TOP=`pwd`
export PATH=$REBAR3_TOP:$PATH

And install:

./bootstrap			

Running the rebar3 command the correct rebar and Erlang version should show up!

rebar3 version

Clone from git:

git clone https://github.com/travelping/ergw		
cd ergw

Compile using rebar3:

rebar3 compile

Modify the configuration of the erGW at ergw/ergw.config and start it (from root):

cd ergw/
sudo erl -setcookie secret -sname ergw -config ergw.config

A default ergw.config can be found here. Try regs() or i(X,Y,Z) with a pid in the shell to check if the processes are running properly.