error installing gem pg version 0.12.2 on Ubuntu 12.04

Question

im running on Ubuntu 12.04 and i'm trying to install the pg gem v '0.12.2' on Ruby 1.9.3p194 / Rails 3.2.3. I have installed libpq-dev and build-essential but i still get the same error:

ERROR:  While executing gem ... (Gem::FilePermissionError)
    You don't have write permissions into the /var/lib/gems/1.9.1 directory.
fernando@ubuntu:/media/fernando/OS/Rails/oops_booking$ sudo gem install pg -v '0.12.2'
Building native extensions.  This could take a while...
ERROR:  Error installing pg:
    ERROR: Failed to build gem native extension.

        /usr/bin/ruby1.9.1 extconf.rb
checking for pg_config... yes
Using config values from /usr/bin/pg_config
checking for libpq-fe.h... yes
checking for libpq/libpq-fs.h... yes
checking for PQconnectdb() in -lpq... yes
checking for PQconnectionUsedPassword()... yes
checking for PQisthreadsafe()... yes
checking for PQprepare()... yes
checking for PQexecParams()... yes
checking for PQescapeString()... yes
checking for PQescapeStringConn()... yes
checking for PQgetCancel()... yes
checking for lo_create()... yes
checking for pg_encoding_to_char()... yes
checking for PQsetClientEncoding()... yes
checking for rb_encdb_alias()... yes
checking for rb_enc_alias()... no
checking for struct pgNotify.extra in libpq-fe.h... yes0
checking for unistd.h... yes
checking for ruby/st.h... yes
creating extconf.h
creating Makefile

make
compiling compat.c
compiling pg.c
pg.c: In function ‘pgconn_wait_for_notify’:
pg.c:2117:3: warning: ‘rb_thread_select’ is deprecated (declared at /usr/include/ruby-1.9.1/ruby/intern.h:379) [-Wdeprecated-declarations]
pg.c: In function ‘pgconn_block’:
pg.c:2592:3: error: format not a string literal and no format arguments [-Werror=format-security]
pg.c:2598:3: warning: ‘rb_thread_select’ is deprecated (declared at /usr/include/ruby-1.9.1/ruby/intern.h:379) [-Wdeprecated-declarations]
pg.c:2607:4: error: format not a string literal and no format arguments [-Werror=format-security]
pg.c: In function ‘pgconn_locreate’:
pg.c:2866:11: warning: variable ‘lo_oid’ set but not used [-Wunused-but-set-variable]
pg.c: In function ‘find_or_create_johab’:
pg.c:3947:3: warning: implicit declaration of function ‘rb_encdb_alias’ [-Wimplicit-function-declaration]
cc1: some warnings being treated as errors
make: *** [pg.o] Error 1

i did install succesfully the newest version of pg gem but i really need to work with the version 0.12.2

thanks in advance

Answer 1

install

$ sudo apt-get install ruby-dev build-essential

or

$ sudo apt-get install postgresql-client libpq5 libpq-dev
$ sudo gem install pg

update

Here are the steps I followed:

Install PostgreSQL and development package

$ sudo apt-get install postgresql-9.1
$ sudo apt-get install libpq-dev

Set up a user that is the same as my Ubuntu log-in

$ sudo su postgres -c psql
postgres=# CREATE ROLE <username> SUPERUSER LOGIN;
postgres=# \q

Modify Gemfile

# Remove gem 'sqlite3'
gem 'pg'

Modify database.yml in app directory

development:
  adapter: postgresql
  encoding: unicode
  database: appname_development
  pool: 5
  timeout: 5000
  username: <username>
  password:

test:
  adapter: postgresql
  encoding: unicode
  database: appname_test
  pool: 5
  timeout: 5000
  username: <username>
  password:

Run bundle install

$ bundle install

Create databases and migrations

$ rake db:create:all
$ rake db:migrate

Here are the sources I used to help:
http://mrfrosti.com/2011/11/postgresql-for-ruby-on-rails-on-ubuntu/
http://railsless.blogspot.in/2012/05/howto-install-postgresql-in-ubuntu11.html