One of the features that RunCloud offers is the ability to create and run containerized servers using Docker, which is a technology that allows you to isolate and package your applications and their dependencies into containers.

However, when you use containerized servers in RunCloud, you need to be aware of how to refer to the host machine and the containers from within your applications.

For example, if you want to install WordPress on a containerized server, you’ll need to specify the database host name in the DB_HOST parameter. Normally, you would use either localhost or to indicate that the database is running on the same machine as the WordPress application.

However, this is not correct for containerized servers, as localhost or would refer to the PHP container that runs WordPress, not the host machine or the MariaDB container that runs the database.

To solve this problem, you need to use a custom value called host for containerized servers. This tells your applications to connect to the host machine, where RunCloud manages the network and port forwarding for your containers. You can also use the host value to connect to other containers on the same server, such as Redis or Memcached.