Create drupal 9 with composer

$ mkdir /home/chiao/public_html/drupal9 

$ composer create-project drupal/recommended-project:~9.0.0\ 

  /home/chiao/public_html/drupal9

Go to /home/chiao/public_html/drupal9/web/sites.

 Copy files to drupal9:
    Custom themes go to /home/chiao/public_html/drupal9/web/themes/custom/
    Custom modules go to /home/chiao/public_html/drupal9/web/modules/custom/
    Libraries go to /home/chiao/public_html/drupal9/web/libraries/
    Your uploaded files and images go to /home/chiao/public_html/drupal9/web/sites/default/files/ 

Copy (using sudo cp -av) the following files and directories to new site:

1. sites/default/settings.php 

2. sites/default/settings.local.php

3. sites/default/files/config_5cKxplPBXz7CfVTT9KjhZ3fJkIg1ygQ2hTdYEM64PUZQUPSy94TTCTcHuJ16-cOW_918dZ1kpw/   asdfsd

4. sites/development.services.yml 

$  cd /home/chiao/public_html/drupal9
$  composer install
All done for creating new drupal 9.