Docker Docker Docker in Production Orchestration Kubernetes Docker Swarm Amazon ECS Azure ACI

1. Core Command / Concept

Orchestration automates container deployment, scaling, and management. docker-compose up.

2. Step-by-Step (numbered)

1. Create a new directory for your project and navigate to it.
   ```bash mkdir myproject cd myproject

2. Create a `docker-compose.yml` file with a basic service definition.
   ```bash
echo "version: '3'
services:
  web:
    image: nginx:latest
    ports:
      - 80:80" > docker-compose.yml

1. Run the service in detached mode.
   ```bash docker-compose up -d

   Output: Service started in detached mode.
4. Check the service status.
   ```bash
docker-compose ps

Output: Service status and container ID.
5. ⚠️ Stop and remove all stopped containers.
```bash docker-compose stop docker-compose rm -f

6. Clean up by removing the `docker-compose.yml` file.
   ```bash
rm docker-compose.yml

3. Real Commands with Examples

Example 1: Deploying a simple web service

• Purpose: Deploy a simple web service using Docker Compose.
• Command: docker-compose up -d
• Brief explanation of flags: -d runs the service in detached mode.

Example 2: Scaling a service

• Purpose: Scale a service to 3 replicas.
• Command: docker-compose up -d --scale web=3
• Brief explanation of flags: --scale sets the number of replicas.

Example 3: Using environment variables

• Purpose: Set environment variables for a service.
• Command: docker-compose up -d -e VIRTUAL_HOST=mydomain.com
• Brief explanation of flags: -e sets an environment variable.

4. Common Errors (3-5)

Error 1: Service not found

• Error message or symptom: docker-compose: error: service "web" not found
• Why it happens: The service is not defined in the docker-compose.yml file.
• One-line fix: docker-compose up -d (create a basic service definition).

Error 2: Port conflict

• Error message or symptom: docker-compose: error: port 80 is already in use
• Why it happens: Another service is using the same port.
• One-line fix: docker-compose up -d --expose 8080 (use a different port).

Error 3: Image not found

• Error message or symptom: docker-compose: error: image "nginx:latest" not found
• Why it happens: The image is not available on Docker Hub.
• One-line fix: docker-compose up -d --build (build the image locally).

5. Quick Checks (3 scenarios)

Scenario 1: Service status

• Situation: Check the status of a service.
• Command: docker-compose ps
• What a correct response looks like: Service status and container ID.

Scenario 2: Container logs

• Situation: Check the logs of a container.
• Command: docker-compose logs web
• What a correct response looks like: Container logs.

Scenario 3: Image list

• Situation: List all images used by a service.
• Command: docker-compose images
• What a correct response looks like: List of images used by the service.

6. Last-Minute Reference

• docker-compose up -d runs the service in detached mode.
• docker-compose ps checks the service status.
• docker-compose logs checks the container logs.
• docker-compose images lists all images used by a service.
• docker-compose rm -f removes all stopped containers.
• docker-compose down stops and removes all containers.
• docker-compose up --build builds the image locally.
• docker-compose config checks the configuration file.
• docker-compose exec runs a command inside a container.
• ⚠️ docker-compose down stops and removes all containers.