Some links

Postgress:

1. Configuration: http://www.iakovlev.org/index.html?p=1431&m=1
2. Book: http://postgresql.leopard.in.ua/html/
3. Replication: http://eax.me/postgresql-replication/

https://habrahabr.ru/post/268631/

Update ruby version on Ubuntu nginx.

> rvm install ruby-2.1.8

> rvm use 2.1.8@xan --create

and

> gem install bundler

Edit nginx.cof

> sudo vi /opt/nginx/conf/nginx.conf

server{

......

   passenger_ruby /home/ubuntu/.rvm/gems/ruby-2.1.8/wrappers/ruby;

   passenger_enabled on;

   rails_env staging;

......

}

restart nginx.