Postgresql is the server running locally and accepting connection on Unix domain

Question

I am trying to install postgresql-9.5 or postgresql-9.6 on my ubuntu 16.04 or 14.04 machine, after following the installation process using below commands.

sudo apt-get install update
sudo apt-get install postgresql postgresql-contrib

But when I am trying to open psql from my terminal using below commands

sudo su postgres 
psql 

every time its just showing.

psql: could not connect to server: No such file or directory Is the server running locally and accepting connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"?

I have tried approximately 10 stackoverflow.com solutions but no success. Please help me out before I tear all my hairs :(

$ service postgresql status

● postgresql.service - PostgreSQL RDBMS
   Loaded: loaded (/lib/systemd/system/postgresql.service; enabled; vendor prese
   Active: active (**exited) since রবি 2017-03-12 21:45:56 BDT; 23min ago
  Process: 917 ExecStart=/bin/true (code=exited, status=0/SUCCESS)
 Main PID: 917 (code=exited, status=0/SUCCESS)
    Tasks: 0
   Memory: 0B
      CPU: 0
   CGroup: /system.slice/postgresql.service

see this line carefully why exited ? Active: active (exited) since রবি 2017-03-12 21:45:56 BDT; 23min ago

Answer 1

You can run the following command to check if postgresql is running:

service postgresql status

If PostgreSQL is not started you can start it with:

service postgresql start
service postgresql status

If it does not start properly, you can look at what is going on in the logs:

tail /var/log/postgresql/postgresql-9.6-main.log

You might have to run createdb to initialize a database (see https://www.postgresql.org/docs/current/static/app-createdb.html):

createdb demo

Update

If PostgreSQL is running when you do service postgresql status but you still can't connect, you should check if PostgreSQL is indeed running on port 5432 or another one with:

netstat -na | grep postgres

Update 2

Since the native packages on debian/ubuntu for PostgreSQL sucks, I advise you to install these instead: https://www.gab.lc/articles/install_postgresql_9-5_debian_ubuntu (replace 9-2 with 9-6).