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Inspect a service on the swarm

When you have deployed a service to your swarm, you can use the Docker CLI to see details about the service running in the swarm.

  1. If you haven’t already, open a terminal and ssh into the machine where you run your manager node. For example, the tutorial uses a machine named manager1.

  2. Run docker service inspect --pretty <SERVICE-ID> to display the details about a service in an easily readable format.

    To see the details on the helloworld service:

    $ docker service inspect --pretty helloworld
    
    ID:     9uk4639qpg7npwf3fn2aasksr
    Name:       helloworld
    Mode:       REPLICATED
     Replicas:      1
    Placement:
    UpdateConfig:
     Parallelism:   1
    ContainerSpec:
     Image:     alpine
     Args:  ping docker.com
    

    Tip: To return the service details in json format, run the same command without the --pretty flag.

    $ docker service inspect helloworld
    [
    {
        "ID": "9uk4639qpg7npwf3fn2aasksr",
        "Version": {
            "Index": 418
        },
        "CreatedAt": "2016-06-16T21:57:11.622222327Z",
        "UpdatedAt": "2016-06-16T21:57:11.622222327Z",
        "Spec": {
            "Name": "helloworld",
            "TaskTemplate": {
                "ContainerSpec": {
                    "Image": "alpine",
                    "Args": [
                        "ping",
                        "docker.com"
                    ]
                },
                "Resources": {
                    "Limits": {},
                    "Reservations": {}
                },
                "RestartPolicy": {
                    "Condition": "any",
                    "MaxAttempts": 0
                },
                "Placement": {}
            },
            "Mode": {
                "Replicated": {
                    "Replicas": 1
                }
            },
            "UpdateConfig": {
                "Parallelism": 1
            },
            "EndpointSpec": {
                "Mode": "vip"
            }
        },
        "Endpoint": {
            "Spec": {}
        }
    }
    ]
    
  3. Run docker service ps <SERVICE-ID> to see which nodes are running the service:

    $ docker service ps helloworld
    
    ID                         NAME          SERVICE     IMAGE   LAST STATE         DESIRED STATE  NODE
    8p1vev3fq5zm0mi8g0as41w35  helloworld.1  helloworld  alpine  Running 3 minutes  Running        worker2
    

    In this case, the one instance of the helloworld service is running on the worker2 node. You may see the service running on your manager node. By default, manager nodes in a Swarm can execute tasks just like worker nodes.

    Swarm also shows you the DESIRED STATE and LAST STATE of the service task so you can see if tasks are running according to the service definition.

  4. Run docker ps on the node where the task is running to see details about the container for the task.

    Tip: If helloworld is running on a node other than your manager node, you must ssh to that node.

    $docker ps
    
    CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
    e609dde94e47        alpine:latest       "ping docker.com"   3 minutes ago       Up 3 minutes                            helloworld.1.8p1vev3fq5zm0mi8g0as41w35
    

What’s next?

Next, you can change the scale for the service running in the swarm.