How CapRover Works

CapRover manages Docker Swarm services on one or more servers.

• CapRover: Stores app configuration, domains, deployment history and settings.
• Docker Swarm: Starts containers, updates service images and maintains requested replicas.
• NGINX: Routes HTTP(S) traffic by hostname to an app's container port.
• Docker registry: Distributes images to nodes in a cluster.
• Volumes and bind mounts: Preserve application data outside replaceable containers.

Applications and services

A CapRover app maps to a Docker Swarm service.

• A web app normally gets <app-name>.<root-domain>.
• Workers and databases can run without public HTTP routing.
• Stateful apps using local storage must stay on the node holding that data.

Builds and deployments

• Deploy an existing image or build one using captain-definition.
• Deployment updates the Docker service to run that image.
• A successful image build does not guarantee a healthy app. The process must listen on the configured container port.
• Image rollbacks do not restore environment variables, database schema or volume contents.

See Deployments and Captain Definition.

Networking

• Public web traffic: DNS → CapRover NGINX → app's HTTP port.
• Internal traffic: Swarm service name and internal port, such as postgres:5432, without publishing a database port.
• Other protocols: Publish TCP/UDP ports explicitly. See Port Reference.

Persistence

• Data written only inside a container can disappear on redeployment.
• Docker volumes and bind mounts are generally node-local. Swarm does not replicate their data.
• Back up app data separately from CapRover's own configuration.

See Persistent Storage.

Docker Swarm

• CapRover initializes a Swarm even for a single-node installation.
• Managers control the Swarm; workers execute assigned tasks.
• Multi-node setups require trusted inter-node networking and a reachable default push registry. See Multi-Node Setup.

Terms

Term	Meaning
captain-definition	Build or image selection file
Root domain	DNS suffix used by the dashboard and default app domains
Instance	A replica of a Docker service
Persistent directory	Docker volume or bind mount inside an app
One-Click App	Template deploying one or more CapRover apps