Install pg gem on CentOS 6

Question

I'm trying to setup my VPS (CentOS 6.4) with ruby on rails and postgres.

I installed ruby (2.1.0p0), rails (4.1.0), and postgresql (9.3.4) with no problem.

When I try create new rails app (rails new new_app -d postgresql) it stops when installing the pg gem. I've looked into all SO posts about this error and tried pretty much everything I could find. The most suggested was to run "yum install postgresql-devel" and still didn't work.

Below you can find the ssh output and the mkmf.log. Let me know if need more information...

---

Output

Building native extensions.  This could take a while...
ERROR:  Error installing pg:
ERROR: Failed to build gem native extension.

/home/deploy/.rvm/rubies/ruby-2.1.0/bin/ruby extconf.rb
checking for pg_config... yes
Using config values from /usr/bin/pg_config
checking for libpq-fe.h... *** 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=/home/deploy/.rvm/rubies/ruby-2.1.0/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}/lib
/home/deploy/.rvm/rubies/ruby-2.1.0/lib/ruby/2.1.0/mkmf.rb:456:in `try_do': The compiler failed to generate an executable file. (RuntimeError)
You have to install development tools first.
    from /home/deploy/.rvm/rubies/ruby-2.1.0/lib/ruby/2.1.0/mkmf.rb:587:in `try_cpp'
    from /home/deploy/.rvm/rubies/ruby-2.1.0/lib/ruby/2.1.0/mkmf.rb:1120:in `block in find_header'
    from /home/deploy/.rvm/rubies/ruby-2.1.0/lib/ruby/2.1.0/mkmf.rb:918:in `block in checking_for'
    from /home/deploy/.rvm/rubies/ruby-2.1.0/lib/ruby/2.1.0/mkmf.rb:351:in `block (2 levels) in postpone'
    from /home/deploy/.rvm/rubies/ruby-2.1.0/lib/ruby/2.1.0/mkmf.rb:321:in `open'
    from /home/deploy/.rvm/rubies/ruby-2.1.0/lib/ruby/2.1.0/mkmf.rb:351:in `block in postpone'
    from /home/deploy/.rvm/rubies/ruby-2.1.0/lib/ruby/2.1.0/mkmf.rb:321:in `open'
    from /home/deploy/.rvm/rubies/ruby-2.1.0/lib/ruby/2.1.0/mkmf.rb:347:in `postpone'
    from /home/deploy/.rvm/rubies/ruby-2.1.0/lib/ruby/2.1.0/mkmf.rb:917:in `checking_for'
    from /home/deploy/.rvm/rubies/ruby-2.1.0/lib/ruby/2.1.0/mkmf.rb:1119:in `find_header'
    from extconf.rb:48:in `'

extconf failed, exit code 1

---

mkmf.log

"gcc -o conftest -I/home/deploy/.rvm/rubies/ruby-2.1.0/include/ruby-2.1.0/x86_64-linux -I/home/deploy/.rvm/rubies/ruby-2.1.0/include/ruby-2.1.0/ruby/backward -I/home/deploy/.rvm/rubies/ruby-2.1.0/include/ruby-2.1.0 -I. -I/usr/include     -O3 -fno-fast-math -ggdb3 -Wall -Wextra -Wno-unused-parameter -Wno-parentheses -Wno-long-long -Wno-missing-field-initializers -Wunused-variable -Wpointer-arith -Wwrite-strings -Wdeclaration-after-statement -Wimplicit-function-declaration  -fPIC conftest.c  -L. -L/home/deploy/.rvm/rubies/ruby-2.1.0/lib -Wl,-R/home/deploy/.rvm/rubies/ruby-2.1.0/lib -L/usr/lib64 -Wl,-R/usr/lib64 -L. -fstack-protector -rdynamic -Wl,-export-dynamic     -Wl,-rpath,'/../lib' -Wl,-R -Wl,'/../lib' -L'/../lib' -lruby  -lpthread -lrt -ldl -lcrypt -lm   -lc"
gcc: error trying to exec 'as': execvp: Permission denied
checked program was:
/* begin */
1: #include "ruby.h"
2:
3: int main(int argc, char **argv)
4: {
5:   return 0;
6: }
/* end */

Answer 1

Before:

For Centos 6: Right install Postgres 9.* with this guide.

After:

yum install postgresql-libs postgresql-devel

Helpful instruction:

How to setup RoR with Postgres

Answer 2

This was easier for me:

ln -s /usr/pgsql-9.5/bin/pg_config /usr/local/bin/

Answer 3

As you are not using the outdated PostgreSQL version that comes with CentOS 6 (PostgreSQL 8.4), you need to install the -devel package matching your version (PostgreSQL 9.X).

The easiest way is to use the official PostgreSQL yum repository.

As the latest version is 9.5 and it is compatible with all 9.X versions I will write the instructions for that one. In the future you can refer to the official instructions for the updated commands.

yum install http://yum.postgresql.org/9.5/redhat/rhel-7-x86_64/pgdg-redhat95-9.5-2.noarch.rpm
yum install postgresql95-devel

Then install the gem with the -with-pg-config option:

gem install pg -- --with-pg-config=/usr/pgsql-9.5/bin/pg_config