Managing Multi-Container Applications Using docker-compose

Podman is included in SLE Micro by default. However, if Podman is missing, you can install it as described below:

The podman-docker is not installed on SLE Micro by default. To install it, proceed as follows:

If docker-compose is not present on your system, you can install it by following the steps:

When defining services, you either need to specify a container image to use, or provide source files to build the service from them.

To create the service container from an image, use the image statement:

      services:
       db:
         image: database

Podman checks if the image name declared in the compose.yml file is available in the local container storage. If it is not, Podman pulls the image from one of the configured registries.

To build a service from source files, provide the source files and create a container file, both in the same directory. In the compose.ymlfile then use the build statement:

      services:
        db: 
          build: PATH_TO_SOURCE_FILES

If a particular service must be started after another, you can use the depends_on statement:

      services:
       db:
         image: database
         depends_on:
          system:
            condition: SERVICE_CONDITION

The SERVICE_CONDITION can be one of the following: service_started, service_healthy or service_completed_successfully.

For more information regarding the services definition, refer to the services specification.

By default, docker-compose creates a default network, and each container in the application stack is included in the network. The default network does not have to be declared in the compose.yml file as docker-compose creates it automatically.

You can also define custom networks and assign particular services to them. For example, to create two networks, network1 and network2, add the following snippet:

networks:
  network1:
    # Use a custom driver
    driver: custom-driver-1
  network2:
    # Use a custom driver and name the network
    driver: custom-driver-2
    name: custom_network

You can also use an existing network. In this case, mark the network as external:

              networks:
  network1:
    name: network1
    external: true

For a complete networks specification, refer to the networks specification.

The following example of compose.yml defines an application stack that uses the Prometheus monitoring system and the Grafana analytics system.

  services:
  prometheus:
    image: prom/prometheus
    container_name: prometheus
    command:
      - '--config.file=/etc/prometheus/prometheus.yml'
    ports:
      - 9090:9090
    restart: unless-stopped
    volumes:
      - ./prometheus:/etc/prometheus
      - prom_data:/prometheus
  grafana:
    image: grafana/grafana
    container_name: grafana
    ports:
      - 3000:3000
    restart: unless-stopped
    environment:
      - GF_SECURITY_ADMIN_USER=admin
      - GF_SECURITY_ADMIN_PASSWORD=grafana
    volumes:
      - ./grafana:/etc/grafana/provisioning/datasources
volumes:
  prom_data:

The project structure in this example must look as follows:

.
├── compose.yaml
├── grafana
│   └── datasource.yml
├── prometheus
│   └── prometheus.yml
└── README.md