[linux] How to configure postgresql for the first time?

I have just installed postgresql and I specified password x during installation. When I try to do createdb and specify any password I get the message:

createdb: could not connect to database postgres: FATAL: password authentication failed for user

Same for createuser.

How should I start? Can I add myself as a user to the database?

There are two methods you can use. Both require creating a user and a database.

1. Using createuser and createdb,

   $ sudo -u postgres createuser --superuser $USER
   $ createdb mydatabase
   $ psql -d mydatabase
   

2. Using the SQL administration commands, and connecting with a password over TCP

   $ sudo -u postgres psql postgres
   

   And, then in the psql shell

   CREATE ROLE myuser LOGIN PASSWORD 'mypass';
   CREATE DATABASE mydatabase WITH OWNER = myuser;
   

   Then you can login,

   $ psql -h localhost -d mydatabase -U myuser -p <port>
   

   If you don't know the port, you can always get it by running the following, as the postgres user,

   SHOW port;
   

   Or,

   $ grep "port =" /etc/postgresql/*/main/postgresql.conf
   

Sidenote: the postgres user

I suggest NOT modifying the postgres user.

1. It's normally locked from the OS. No one is supposed to "log in" to the operating system as postgres. You're supposed to have root to get to authenticate as postgres.
2. It's normally not password protected and delegates to the host operating system. This is a good thing. This normally means in order to log in as postgres which is the PostgreSQL equivalent of SQL Server's SA, you have to have write-access to the underlying data files. And, that means that you could normally wreck havoc anyway.
3. By keeping this disabled, you remove the risk of a brute force attack through a named super-user. Concealing and obscuring the name of the superuser has advantages.

EDIT: Warning: Please, read the answer posted by Evan Carroll. It seems that this solution is not safe and not recommended.

This worked for me in the standard Ubuntu 14.04 64 bits installation.

I followed the instructions, with small modifications, that I found in http://suite.opengeo.org/4.1/dataadmin/pgGettingStarted/firstconnect.html

1. Install postgreSQL (if not already in your machine):

sudo apt-get install postgresql

2. Run psql using the postgres user

sudo –u postgres psql postgres

3. Set a new password for the postgres user:

\password postgres

4. Exit psql

\q

5. Edit /etc/postgresql/9.3/main/pg_hba.conf and change:

#Database administrative login by Unix domain socket local all postgres peer

To:

#Database administrative login by Unix domain socket local all postgres md5

6. Restart postgreSQL:

sudo service postgresql restart

7. Create a new database

sudo –u postgres createdb mytestdb

8. Run psql with the postgres user again:

psql –U postgres –W

9. List the existing databases (your new database should be there now):

\l

If you're running macOS like I am, you may not have the postgres user.

When trying to run sudo -u postgres psql I was getting the error sudo: unknown user: postgres

Luckily there are executables that postgres provides.

createuser -D /var/postgres/var-10-local --superuser --username=nick
createdb --owner=nick

Then I was able to access psql without issues.

psql
psql (10.2)
Type "help" for help.

nick=#

If you're creating a new postgres instance from scratch, here are the steps I took. I used a non-default port so I could run two instances.

mkdir /var/postgres/var-10-local
pg_ctl init -D /var/postgres/var-10-local

Then I edited /var/postgres/var-10-local/postgresql.conf with my preferred port, 5433.

/Applications/Postgres.app/Contents/Versions/10/bin/postgres -D /Users/nick/Library/Application\ Support/Postgres/var-10-local -p 5433

createuser -D /var/postgres/var-10-local --superuser --username=nick --port=5433
createdb --owner=nick --port=5433

Done!

In MacOS, I followed the below steps to make it work.

For the first time, after installation, get the username of the system.

$ cd ~
$ pwd
/Users/someuser
$ psql -d postgres -U someuser

Now that you have logged into the system, and you can create the DB.

postgres=# create database mydb;
CREATE DATABASE
postgres=# create user myuser with encrypted password 'pass123';
CREATE ROLE
postgres=# grant all privileges on database mydb to myuser;
GRANT

This is my solution:

su root
su postgres
psql

Note: textdb is the database which you are going to explore with 'alex' user 

root@kalilinux:~# sudo su - postgres 
postgres=#  psql   
postgres=#  create database testdb;
postgres=#  create user alex with password 'alex';
postgres=# GRANT ALL PRIVILEGES ON DATABASE testdb TO alex;`enter code here`

Under Linux PostgresQL is usually configured to allow the root user to login as the postgres superuser postgres from the shell (console or ssh).

$ psql -U postgres

Then you would just create a new database as usual:

CREATE ROLE myuser LOGIN password 'secret';
CREATE DATABASE mydatabase ENCODING 'UTF8' OWNER myuser;

This should work without touching pg_hba.conf. If you want to be able to do this using some GUI tool over the network - then you would need to mess with pg_hba.conf.

Just browse up to your installation's directory and execute this file "pg_env.bat", so after go at bin folder and execute pgAdmin.exe. This must work no doubt!

You probably need to update your pg_hba.conf file. This file controls what users can log in from what IP addresses. I think that the postgres user is pretty locked-down by default.