Installing Postgres

Linux Windows 

$ sudo apt install postgresql postgresql-contrib
$ sudo apt install libpq-dev
$ psql --version
$ sudo service postgresql status
$ sudo netstat -plunt |grep postgres    //Check port
tcp        0      0 127.0.0.1:5432          0.0.0.0:*               LISTEN      255/postgres        
$
Install Postgres on Windows

Create user, Login with User

When installing postgres on Windows/Linux, Installation scripts creates a local user=postgres, but inside postgres there is a seperate user called postgres.
Purpose of Local postgres user is to login postgres DB, then change the password of DB(internal's postgres user). Since all database operations are carried using DB's internal postgres user.
Linux Windows 

# cat /etc/passwd|grep postgres
postgres:x:105:109:PostgreSQL administrator,,,:/var/lib/postgresql:/bin/bash

// Change passwd Unix postgres user
$ sudo passwd postgres  //Change Unix password of postgres user
new password:
Retype new password:


// Change authentication from peer to md5(to accept password to connect)
$ sudo vim /etc/postgresql/14/main/pg_hba.conf 
#local   all             postgres                                peer
local   all             postgres                                md5
$ sudo systemctl restart postgresql

// Login to postgres using local postgres user
$ sudo -u postgres psql
postgres=#

// Change password of DB(internal user=postgres)
postgres=# ALTER USER postgres WITH PASSWORD 'NEW PASSWORD';
ALTER ROLE
postgres=# \q

// Check Login to postgres using DB's(Internal postgres user)
$ psql -U postgres -W
Password: <NEW PASSWORD>

          

// Port provided at time of installation
C:\Users\user> netstat -ant | find "5432"
TCP    0.0.0.0:5432           0.0.0.0:0              LISTENING       InHost
TCP    [::]:5432              [::]:0                 LISTENING       InHost


// During installtion postgres creates user=postgres
// password is provided during installation only
C:\Users\user> psql -U postgres
Password for user postgres:

psql (17.3)
WARNING: Console code page (437) differs from Windows code page (1252)
         8-bit characters might not work correctly. See psql reference
         page "Notes for Windows users" for details.
Type "help" for help.

postgres=#