rake db:create password authentication fails for user - ruby-on-rails

Question

While running the command rake db:create, the system throws postgresql authentication fails
FATAL: password authentication failed for user "postgres"
Couldn't create database for {"adapter"=>"postgresql", "encoding"=>"unicode", "pool"=>5, "username"=>"postgres", "password"=>"password", "timeout"=>5000, "host"=>"localhost", "database"=>"rails-sample-guestbook-master_development"}
rake aborted!
database.yml file
default: &default
adapter: postgresql
encoding: unicode
pool: 5
username: supranimbus
password: 123456789
timeout: 5000
host: localhost
development:
<<: *default
database: rails-sample-guestbook-master_development
test:
<<: *default
database: rails-sample-guestbook-master_test
production:
<<: *default
database: rails-sample-guestbook-master_production

Answer 1

I guess the problem is setup password on postgresql if you don't remember the default password then go to pgAdmin click to open dashboard and then the left sidebar see the below image
Click the Properties... then will open a modal like see the below image
and click the Definition tab and see the Password field and set the new password, remember this password for postgres username.
That's is for password setup!
Now update your database.yml file like below
default: &default
adapter: postgresql
encoding: unicode
username: postgres
password: 123456 #=> which you set for postgres
pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
development:
<<: *default
database: project_development
Hope to help