postgresql on Arch/Manjaro

Install: pacman -S postgresql
= this will create user "postgres"

Then: sudo passwd postgres
= choose a password

Then switch to postgres user using:

sudo -iu postgres

Then: 
[postgres]$ initdb -D /var/lib/postgres/data

Then: 

systemctl enable postgresql 

and

systemctl start postgresql

Then 

Become the postgres user.

sudo -iu postgres

Add a new database user using the createuser command:
[postgres]$ createuser --interactive

Create a new database over which the above user has read/write privileges using the createdb command (execute this command from your login shell if the database user has the same name as your Linux user, otherwise add -O database-username to the following command):

$ createdb myDatabaseName

Then to connect:

[postgres]$ psql -d myDatabaseName

Some helpful commands:
Get help:
=> \help Connect to a particular database:
=> \c <database> List all users and their permission levels:
=> \du Show summary information about all tables in the current database:
=> \dt Exit/quit the psql shell:
=> \q or CTRL+d

sources http://www.postgresqltutorial.com/postgresql-uuid/

Add the UUID plugin:
CREATE EXTENSION IF NOT EXISTS "uuid-ossp";
Test it with:
SELECT uuid_generate_v1();