Some JAMs (Janitor modules) require libraries that are typically installed via Composer. In order for these modules to install correctly, Composer must be available on the server.

To install Composer in a compatible way, follow these instructions.

Locate the latest Composer install instructions on the Composer homepage: https://getcomposer.org/download/

Follow the instructions to install Composer in any directory of your choosing.

After installation, move composer.phar to a globally available location, so that the Janitor module install will be able to find it:

sudo mv composer.phar /usr/local/bin

That's it.