Agent Mode

Dozzle can run in agent mode which can expose Docker hosts to other Dozzle instances. All communication is done over a secured connection using TLS. This means that you can deploy Dozzle on a remote host and connect to it from your local machine.

Using Docker Swarm?

If you are using Docker Swarm Mode, you don't need to use agents. Dozzle will automatically discover itself and create a cluster using swarm mode. See Swarm Mode for more information.

How to Create an Agent

To create a Dozzle agent, you need to run Dozzle with the agent subcommand. Here is an example:

sh

docker run -v /var/run/docker.sock:/var/run/docker.sock -p 7007:7007 amir20/dozzle:latest agent

docker-compose.yml

services:
  dozzle-agent:
    image: amir20/dozzle:latest
    command: agent
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock:ro
    ports:
      - 7007:7007

The agent will start and listen on port 7007. You can connect to the agent using the Dozzle UI by providing the agent's IP address and port. The agent will only show the containers that are available on the host where the agent is running.

TIP

You don't need to expose port 7007 if using Docker network. The agent will be available to other containers on the same network.

How to Connect to an Agent

To connect to an agent, you need to provide the agent's IP address and port. Here is an example:

sh

docker run -p 8080:8080 amir20/dozzle:latest --remote-agent agent-ip:7007

docker-compose.yml

services:
  dozzle:
    image: amir20/dozzle:latest
    environment:
      - DOZZLE_REMOTE_AGENT=agent:7007
    ports:
      - 8080:8080 # Dozzle UI port

Note that when connecting remotely, you don't need to mount local Docker socket. The UI will only show the containers that are available on the agent.

TIP

You can connect to multiple agents by providing multiple DOZZLE_REMOTE_AGENT environment variables. For example, DOZZLE_REMOTE_AGENT=agent1:7007,agent2:7007.

WARNING

Dozzle uses the Docker API to gather information about hosts. Each agent needs a unique host ID. They use Docker's system ID or node ID to identify the host. If you are using swarm, then the node ID is used. If you don't see all hosts, then you may have duplicate hosts configured that have the same host ID. To fix this, remove /var/lib/docker/engine-id file. See FAQ for more information.

Setting Up Healthcheck

You can set a healthcheck for the agent, similar to the healthcheck for the main Dozzle instance. When running in agent mode, healthcheck checks agent connection to Docker. If Docker is not reachable, the agent will be marked as unhealthy and will not be shown in the UI.

To set up healthcheck, use the healthcheck subcommand. Here is an example:

services:
  dozzle-agent:
    image: amir20/dozzle:latest
    command: agent
    healthcheck:
      test: ["CMD", "/dozzle", "healthcheck"]
      interval: 5s
      retries: 5
      start_period: 5s
      start_interval: 5s
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock:ro
    ports:
      - 7007:7007

Changing Agent's Name

Similar to Dozzle instance, you can change the agent's name by providing the DOZZLE_HOSTNAME environment variable. Here is an example:

sh

docker run -v /var/run/docker.sock:/var/run/docker.sock -p 7007:7007 amir20/dozzle:latest agent --hostname my-special-name

docker-compose.yml

services:
  dozzle-agent:
    image: amir20/dozzle:latest
    command: agent
    environment:
      - DOZZLE_HOSTNAME=my-special-name
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock:ro
    ports:
      - 7007:7007

This will change the agent's name to my-special-name and will be reflected on the UI when connecting to the agent.

Custom Certificates

By default, Dozzle uses self-signed certificates for communication between agents. This is a private certificate which is only valid to other Dozzle instances. This is secure and recommended for most use cases. However, if Dozzle is exposed externally and an attacker knows exactly which port the agent is running on, then they can set up their own Dozzle instance and connect to the agent. To prevent this, you can provide your own certificates.

To provide custom certificates, you need to mount or use secrets to provide the certificates. Here is an example:

services:
  agent:
    image: amir20/dozzle:latest
    command: agent
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock
    secrets:
      - source: cert
        target: /dozzle_cert.pem
      - source: key
        target: /dozzle_key.pem
    ports:
      - 7070:7070
secrets:
  cert:
    file: ./cert.pem
  key:
    file: ./key.pem

TIP

Docker secrets are preferred for providing certificates. They can be created using docker secret create command or as the example above using docker-compose.yml. The same certificates should be provided to the Dozzle instance connecting to the agent.

This will mount the cert.pem and key.pem files to the agent. The agent will use these certificates for communication. The same certificates should be provided to the Dozzle instance connecting to the agent.

To generate certificates, you can use the following command:

$ openssl genpkey -algorithm RSA -out key.pem -pkeyopt rsa_keygen_bits:2048
$ openssl req -new -key key.pem -out request.csr -subj "/C=US/ST=California/L=San Francisco/O=My Company"
$ openssl x509 -req -in request.csr -signkey key.pem -out cert.pem -days 365

Comparing Agents with Remote Connection

Agents are similar to remote connections, but they have some advantages. Generally, agents are preferred over remote connections due to performance and security reasons. Here is a comparison:

Feature	Agent	Remote Connection
Performance	Better with distributed load	Worse on the UI
Security	Private SSL	Insecure or Docker TLS
Ease of use	Easy out of the box	Requires exposing Docker socket
Permissions	Full access to Docker	Can be controlled with a proxy
Reconnect	Automatically reconnects	Requires UI restart
Healthcheck	Built-in healthcheck	No healthcheck

If you do plan to use remote connections, make sure to secure the connection using Docker TLS or a reverse proxy.