[root@db console]# bundle install
    Don't run Bundler as root. Bundler can ask for sudo if it is needed, and installing your bundle as root will break this application for all non-root users on this machine.
    Fetching gem metadata from https://rubygems.org/.........
    Fetching additional metadata from https://rubygems.org/..
    Using rake 10.1.0
    Using i18n 0.6.5
    Using minitest 4.7.5
    Using multi_json 1.7.9
    Using atomic 1.1.13
    Using thread_safe 0.1.2
    Using tzinfo 0.3.37
    Using activesupport 4.0.0
    Using builder 3.1.4
    Using erubis 2.7.0
    Using rack 1.5.2
    Using rack-test 0.6.2
    Using actionpack 4.0.0
    Using mime-types 1.24
    Using polyglot 0.3.3
    Using treetop 1.4.14
    Using mail 2.5.4
    Using actionmailer 4.0.0
    Using activemodel 4.0.0
    Using activerecord-deprecated_finders 1.0.3
    Using arel 4.0.0
    Using activerecord 4.0.0
    Using coffee-script-source 1.6.3
    Using execjs 1.4.0
    Using coffee-script 2.2.0
    Using thor 0.18.1
    Using railties 4.0.0
    Using coffee-rails 4.0.0
    Using daemons 1.1.9
    Using eventmachine 1.0.3
    Using hike 1.2.3
    Using jquery-rails 3.0.4
    Using json 1.8.0

    Gem::Ext::BuildError: ERROR: Failed to build gem native extension.

        /usr/local/rvm/rubies/ruby-2.0.0-p451/bin/ruby extconf.rb
    checking for pg_config... no
    No pg_config... trying anyway. If building fails, please try again with
     --with-pg-config=/path/to/pg_config
    checking for libpq-fe.h... no
    Can't find the 'libpq-fe.h header
    *** extconf.rb failed ***
    Could not create Makefile due to some reason, probably lack of necessary
    libraries and/or headers.  Check the mkmf.log file for more details.  You may
    need configuration options.

    Provided configuration options:
            --with-opt-dir
            --without-opt-dir
            --with-opt-include
            --without-opt-include=${opt-dir}/include
            --with-opt-lib
            --without-opt-lib=${opt-dir}/lib
            --with-make-prog
            --without-make-prog
            --srcdir=.
            --curdir
            --ruby=/usr/local/rvm/rubies/ruby-2.0.0-p451/bin/ruby
            --with-pg
            --without-pg
            --with-pg-config
            --without-pg-config
            --with-pg_config
            --without-pg_config
            --with-pg-dir
            --without-pg-dir
            --with-pg-include
            --without-pg-include=${pg-dir}/include
            --with-pg-lib
            --without-pg-lib=${pg-dir}/

    extconf failed, exit code 1

    Gem files will remain installed in /usr/local/rvm/gems/ruby-2.0.0-p451/gems/pg-0.16.0 for inspection.
    Results logged to /usr/local/rvm/gems/ruby-2.0.0-p451/extensions/x86_64-linux/2.0.0/pg-0.16.0/gem_make.out
    An error occurred while installing pg (0.16.0), and Bundler cannot continue.
    Make sure that `gem install pg -v '0.16.0'` succeeds before bundling.
[root@db console]# locate pg_config
/usr/pgsql-9.1/bin/pg_config