Installing PostgreSQL 9.2 on Ubuntu 12.04 for rails development

psql-9.2-ubuntu-12.04.txt

# Installing PostgreSQL 9.2 on Ubuntu 12.04 for rails development


#Add repo
sudo apt-get -y install python-software-properties
sudo add-apt-repository ppa:pitti/postgresql
sudo apt-get update


#install psql 9.2 and libpq 
sudo apt-get -y install postgresql-9.2 postgresql-client-9.2 postgresql-contrib-9.2
sudo apt-get -y install postgresql-server-dev-9.2 libpq-dev


# After Installation Log into the postgresql prompt before that set up a password for psql 
sudo passwd postgres


# Enter the psql command prompt
su - postgres


# create db 
createdb dbname


#drop db
dropdb dbname


#list all database
psql -l


# Now create the user for a database to be used for your project for my case its geomap
# P-  issue a prompt for the password
# d- create a db of same name as user
# a- allow user to add new users (superuser)
# e- Echo the commands that createuser generates and sends to the server.
createuser -P -d -a -e geomap


#In case you want to create another db with this owner(user)
createdb geomap_development --owner=geomap


#Now into your rails app (mine is running on rails 3.2.13 with ruby 1.9.2) Add the gem pg into the Gemfile and install it by bundler
#Make sure you have the database created before you fill in the details here. for production please refer to a more detailed process 
#For postgresql the config/database.yml file looks like this
development:
  adapter: postgresql
  encoding: utf8
  database: geomap_development
  username: geomap 
  password: xxxx
  host: localhost

test:
  adapter: postgresql
  encoding: utf8
  database: geomap_test
  username: geomap 
  password: xxxx
  host: localhost

production:
  adapter: postgresql
  encoding: utf8
  database: geomap_test
  username: geomap
  password: xxxx 
  host: localhost

#Now in the folder of your rails app:
~/geomap$ rake db:migrate

# restart the server
----------------------------------------------------------------------------
# Trouble shooting
1. In case you have to remove postgres 9.2 

Ans: 

# List all the postgresql installs running on the system
dpkg -l | grep postgres

# Remove postgres 
sudo apt-get --purge remove postgresql-9.2 postgresql-client-9.2 postgresql-contrib-9.2

# Remove individual postgres folders
sudo rm -rf /var/lib/postgresql/
sudo rm -rf /etc/postgresql 

# Rerun the command given below and it should return nothing
dpkg -l | grep postgres

#delete users and groups if any; if /var/lib/postgresql folder is deleted the users and groups are deleted.
sudo userdel -r postgres
sudo groupdel -r postgres

2. During reinstallation If you fail with 
Creating new cluster (configuration: /etc/postgresql/9.2/main, data: /var/lib/postgresql/9.2/main)...
FATAL:  could not create shared memory segment: Invalid argument
DETAIL:  Failed system call was shmget(key=1, size=1835008, 03600).
Usually Hint will tell you that Shared kernel memory is zero shmmax

Ans:
#run the command given below and look for shmmax
sysctl -a | grep shm

# If kernel.shmmax=0 then edit /etc/sysctl.conf and set kernel.shmmax = 2147483648 
#Please read the literature before setting shmmax values for your kernel and refer to other sources. 

#Restart the system configuration setting
sudo /sbin/sysctl -p

#create pg_cluster
sudo pg_createcluster 9.2 main --start


sources: 
1. Chen https://gist.github.com/chen206/4030441 Use it for detailed installation 
2. PostgreSQL 9.2 Documentation
3. stackoverflow