How to install pg gem in rails - ruby-on-rails

Question

I tried to install pg gem. But it produce the following error. Can anyone help me to solve this problem ?
root#localhost:/home/rails/Project# gem install pg
Building native extensions. This could take a while...
ERROR: Error installing pg:
ERROR: Failed to build gem native extension.
current directory: /var/lib/gems/2.3.0/gems/pg-0.18.4/ext
/usr/bin/ruby2.3 -r ./siteconf20160908-9582-xu3pmx.rb extconf.rb
checking for pg_config... yes
Using config values from /usr/bin/pg_config
You need to install postgresql-server-dev-X.Y for building a server-side extension or libpq-dev for building a client-side application.
You need to install postgresql-server-dev-X.Y for building a server-side extension or libpq-dev for building a client-side application.
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/bin/$(RUBY_BASE_NAME)2.3
--with-pg
--without-pg
--enable-windows-cross
--disable-windows-cross
--with-pg-config
--without-pg-config
--with-pg_config
--without-pg_config
--with-pg-dir
--without-pg-dir
--with-pg-include
--without-pg-include=${pg-dir}/include
--with-pg-lib
--without-pg-lib=${pg-dir}/lib
To see why this extension failed to compile, please check the mkmf.log which can be found here:
/var/lib/gems/2.3.0/extensions/x86-linux/2.3.0/pg-0.18.4/mkmf.log
extconf failed, exit code 1
Gem files will remain installed in /var/lib/gems/2.3.0/gems/pg-0.18.4 for inspection.
Results logged to /var/lib/gems/2.3.0/extensions/x86-linux/2.3.0/pg-0.18.4/gem_make.out
root#localhost:/home/rails/Project#

Answer 1

The error says:
You need to install postgresql-server-dev-X.Y
for building a server-side extension
or libpq-dev for building a client-side application.
checking for libpq-fe.h... no
Can't find the 'libpq-fe.h header
*** extconf.rb failed ***
It's a good skill to read errors from the building native extensions step of a gem installation. Native extensions frequently depend on system libraries which won't be automatically installed.
you need to run apt-get install libpq-dev
See here for a good guide to install Postgres on Ubuntu - there are more steps than just installing the gem. You'll need to configure a postgres user account as well.