Composer
Manage custom package using composer.
Composer can hadle CVS (git, svn ...) and ZIP packages.
To install/Update your custom modules, add a custom repository to the composer.json file, following this example.
1. Add package repositories
Here, youtubeapi and sadb
Create a Drupal 9 Project using composer.
Using recommended-project template
composer create-project drupal/recommended-project my-project
For more information, see : https://www.drupal.org/docs/develop/using-composer/starting-a-site-using-drupal-composer-project-templates
Install and Update Composer
Install Composer
wget https://getcomposer.org/installer
php installer
unlink installersudo mv composer.phar /usr/local/bin/composer.phar
alias composer='/usr/local/bin/composer.phar'
Get composer instalation path
Run : which composer
Result exemple : /usr/local/bin/composer