Why use the Portainer Agent?

Purpose of the Portainer Agent

Docker Swarm introduces the concept of clustering nodes into a 'Swarm' and brings services, tasks, configs and secrets as cluster-aware resources. Cluster-aware means that you can ask for a list of services or look at a task inside any node on the cluster, as long as you’re operating from a 'manager' node.

Thus we have found a limitation of Docker: containers, networks, volumes and images are node specific resources, not cluster-aware. So when you want to list all of containers, networks etc inside your cluster, you are not able to, you can only ask a specific node for a list of its resources. When running the Agent however, you can treat containers, networks, volumes and images as cluster-aware resources.

This means you can now use Portainer to access all of the containers, volumes, networks etc in your entire cluster.