Docker Docker Docker in Production Docker Swarm Basics init join service stack configs secrets

1. Core Command / Concept

Create a Docker Swarm cluster by initializing a manager node and joining worker nodes. docker swarm init

2. Step-by-Step

1. Check if Docker is installed and running: docker --version
2. Initialize a Docker Swarm cluster: docker swarm init --advertise-addr <manager-ip>
3. Output: Swarm initialized, manager is
4. Clean up: docker swarm leave
5. ⚠️ Delete all stopped containers: docker container prune -f
6. Join a worker node to the Swarm cluster: docker swarm join --token <token> <manager-ip>:2377
7. Output: This node joined a swarm as a worker.
8. Clean up: docker swarm leave
9. Create a new service: docker service create --name <service-name> <image-name>
10. Output: Service created
11. Clean up: docker service rm <service-name>
12. Create a new stack: docker stack deploy --compose-file <compose-file> <stack-name>
13. Output: Stack created
14. Clean up: docker stack rm <stack-name>

3. Real Commands with Examples

Example 1: Create a service

• Purpose: Run a web server on port 80
• Command: docker service create --name web-server --publish 80:80 nginx
• Brief explanation of flags: --name sets the service name, --publish maps port 80 on the host to port 80 in the container

Example 2: Create a stack

• Purpose: Run a web server and a database on separate containers
• Command: docker stack deploy --compose-file docker-compose.yml web-app
• Brief explanation of flags: --compose-file specifies the Docker Compose file to use, --name sets the stack name

Example 3: Create a config

• Purpose: Set environment variables for a service
• Command: docker config create --label <label> <config-name> <config-value>
• Brief explanation of flags: --label sets a label for the config, --name sets the config name

4. Common Errors

Error 1: Swarm mode not enabled

• Error message or symptom: Error response from daemon: Swarm is not initialized.
• Why it happens: Docker Swarm is not enabled
• One-line fix: docker swarm init

Error 2: Service not created

• Error message or symptom: Error response from daemon: Service not found: <service-name>
• Why it happens: Service does not exist
• One-line fix: docker service create --name <service-name> <image-name>

Error 3: Config not found

• Error message or symptom: Error response from daemon: Config not found: <config-name>
• Why it happens: Config does not exist
• One-line fix: docker config create --name <config-name> <config-value>

5. Quick Checks

Scenario 1: Check if Swarm is initialized

• Situation: You want to check if Docker Swarm is initialized
• Command to run: docker info
• What a correct response looks like: Swarm: active

Scenario 2: Check if service is running

• Situation: You want to check if a service is running
• Command to run: docker service ps <service-name>
• What a correct response looks like: Name and Status columns with running services

Scenario 3: Check if config exists

• Situation: You want to check if a config exists
• Command to run: docker config ls
• What a correct response looks like: ID and Name columns with existing configs

6. Last-Minute Reference

• docker swarm init: Initialize a Docker Swarm cluster
• docker swarm join: Join a worker node to the Swarm cluster
• docker service create: Create a new service
• docker stack deploy: Create a new stack
• docker config create: Create a new config
• docker config rm: Remove a config
• docker service rm: Remove a service
• docker stack rm: Remove a stack
• docker swarm leave: Leave the Swarm cluster
• docker container prune: Remove stopped containers
• docker system prune: Remove unused data
• ⚠️ docker swarm init --advertise-addr : Specify the manager IP address
• ⚠️ docker swarm join --token :2377: Specify the join token and manager IP address
• ⚠️ docker config create --label : Specify the config label and value