Ubuntu 22.04 postgres setup without password same as how OSx has it

when you develop Rails app on OSx Postgresql it's default that user don't need password to create DB so your database.yml may look like

default: &default
  adapter: postgresql
  encoding: unicode
  pool: 5

development:
  <<: *default
  database: myapp_development
  host: localhost

..so no user no pass

Problem is that Ubuntu Postgres (installed with standard $sudo apt-get install postgresql postgresql-contrib libpq-dev )

is more strict and requires password auth so when you run

rails db:create

you will get error

ActiveRecord::ConnectionNotEstablished: connection to server at "127.0.0.1", port 5432 failed: fe_sendauth: no password supplied (ActiveRecord::ConnectionNotEstablished)

in order to get around this you need to edit file

 sudo vim /etc/postgresql/14/main/pg_hba.conf

and have values like this

 # Database administrative login by Unix domain socket
 local   all             all                                     trust

 # TYPE  DATABASE        USER            ADDRESS                 METHOD

 # "local" is for Unix domain socket connections only
 local   all             all                                     trust
 # IPv4 local connections:
 host    all             all             127.0.0.1/32            trust
 # IPv6 local connections:
 host    all             all             ::1/128                 trust

After save

sudo service postgresql restart

credit https://gist.github.com/p1nox/4953113

Now if you run

rails db:create

you get new error

PG::ConnectionBad: connection to server at "127.0.0.1", port 5432 failed: FATAL:  role "thisisyou" does not exist (PG::ConnectionBad)

thisisyou is your Ubuntu user, without specifying an user in database.yml Ubuntu will use system user name as postgres user = we need to create postgres user

sudo -u postgres psql

then

CREATE USER thisisyou WITH PASSWORD '';
ALTER USER thisisyou WITH SUPERUSER'