After setting up Manjaro on my new working laptop, I installed PostgreSQL 9.4. When I want to start the service by running sudo systemctl start postgresql, postgresql keep failing to start.

Apparently before PostgreSQL can function correctly on Arch Linux based distro, the database cluster must be initialized by the postgres user. Fix this just by running the following command:

sudo -i -u postgres
initdb --locale en_US.UTF-8 -E UTF8 -D '/var/lib/postgres/data'