Enabling TLS encryption for communication between Docker Swarm

1. Generate TLS Certificates:

• Generate TLS certificates for each Docker Swarm node. You can use tools like OpenSSL to generate self-signed certificates or use a certificate authority (CA) to issue certificates.
• Ensure that each certificate includes the necessary Subject Alternative Names (SANs) for IP addresses and hostnames of Docker Swarm nodes.

2. Configure Docker Daemon:

• Edit the Docker daemon configuration file (/etc/docker/daemon.json on Linux).
• Add the following TLS-related configuration options:

{
  "tls": true,
  "tlscacert": "/path/to/ca.pem",
  "tlscert": "/path/to/server-cert.pem",
  "tlskey": "/path/to/server-key.pem",
  "tlsverify": true
}

• tlscacert: Path to the CA certificate file.
• tlscert: Path to the node's certificate file.
• tlskey: Path to the node's private key file.
• tlsverify: Enable TLS verification.

3. Restart Docker Daemon:

• Restart the Docker daemon to apply the changes:

sudo systemctl restart docker

4. Join Nodes to Swarm:

• When joining nodes to the Docker Swarm, specify the TLS options using the --tlsverify, --tlscacert, --tlscert, and --tlskey flags.

docker swarm join --token <token> <manager-ip:port> --tlsverify --tlscacert /path/to/ca.pem --tlscert /path/to/node-cert.pem --tlskey /path/to/node-key.pem

5. Verify TLS Encryption:

• After configuring TLS encryption, verify that communication between Docker Swarm nodes is encrypted using TLS.
• You can use network sniffing tools like Wireshark to capture network traffic and verify that it’s encrypted.

By following these steps, you can enable TLS encryption for communication between Docker Swarm nodes, enhancing the security of your Docker Swarm cluster.