Docker "Hello World" Example

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Pre-requisite

Create an account with DockerHub
Open PWD Platform on your browser
Click on Add New Instance on the left side of the screen to bring up Alpine OS instance on the right side

Running Hello World Example

$ docker run hello-world

alt text

Explanation

This image is a prime example of using the scratch image effectively. See hello.c in https://github.com/docker-library/hello-world for the source code of the hello binary included in this image.

So what’s happened here? We’ve called the docker run command, which is responsible for launching containers.

The argument hello-world is the name of the image someone created on dockerhub for us. It will first search for “hello-world” image locally and then search in Dockerhub.

Once the image has been downloaded, Docker turns the image into a running container and executes it.

Did you Know?

The Hello World Docker Image is only 1.84 KB size.

[node1] (local) root@192.168.0.18 ~
$ docker images
REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
hello-world         latest              4ab4c602aa5e        6 weeks ago         1.84kB

While running docker ps command, it doesn’t display any running container. Reason – It gets executed once and exit immediately.

$ docker ps
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS
      PORTS               NAMES

You can use docker inspect <imagename> command to inspect about this particular Docker Image.

$ docker inspect 4ab
[
    {
        "Id": "sha256:4ab4c602aa5eed5528a6620ff18a1dc4faef0e1ab3a5eddeddb410714478c67f",
        "RepoTags": [
            "hello-world:latest"
        ],
        "RepoDigests": [
            "hello-world@sha256:0add3ace90ecb4adbf7777e9aacf18357296e799f81cabc9fde470971e499788"
        ],
        "Parent": "",
        "Comment": "",
        "Created": "2018-09-07T19:25:39.809797627Z",
        "Container": "15c5544a385127276a51553acb81ed24a9429f9f61d6844db1fa34f46348e420",
        "ContainerConfig": {
            "Hostname": "15c5544a3851",
            "Domainname": "",
            "User": "",
            "AttachStdin": false,
            "AttachStdout": false,
            "AttachStderr": false,
            "Tty": false,
            "OpenStdin": false,
            "StdinOnce": false,
            "Env": [
                "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
            ],
            "Cmd": [
                "/bin/sh",
                "-c",
                "#(nop) ",
                "CMD [\"/hello\"]"
            ],
            "ArgsEscaped": true,
            "Image": "sha256:9a5813f1116c2426ead0a44bbec252bfc5c3d445402cc1442ce9194fc1397027",
            "Volumes": null,
            "WorkingDir": "",
            "Entrypoint": null,
            "OnBuild": null,
            "Labels": {}
        },
        "DockerVersion": "17.06.2-ce",
        "Author": "",
        "Config": {
            "Hostname": "",
            "Domainname": "",
            "User": "",
            "AttachStdin": false,
            "AttachStdout": false,
            "AttachStderr": false,
            "Tty": false,
            "OpenStdin": false,
            "StdinOnce": false,
            "Env": [
                "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
            ],
            "Cmd": [
                "/hello"
            ],
            "ArgsEscaped": true,
            "Image": "sha256:9a5813f1116c2426ead0a44bbec252bfc5c3d445402cc1442ce9194fc1397027",
            "Volumes": null,
            "WorkingDir": "",
            "Entrypoint": null,
            "OnBuild": null,
            "Labels": null
        },
        "Architecture": "amd64",
        "Os": "linux",
        "Size": 1840,
        "VirtualSize": 1840,
        "GraphDriver": {
            "Data": {
                "MergedDir": "/var/lib/docker/overlay2/e494ae30abc49ad403ef5c2a32bcb894629ea4da6d4d226fbca70d27ed9a74d8/merged",
                "UpperDir": "/var/lib/docker/overlay2/e494ae30abc49ad403ef5c2a32bcb894629ea4da6d4d226fbca70d27ed9a74d8/diff",
                "WorkDir": "/var/lib/docker/overlay2/e494ae30abc49ad403ef5c2a32bcb894629ea4da6d4d226fbca70d27ed9a74d8/work"
            },
            "Name": "overlay2"
        },
        "RootFS": {
            "Type": "layers",
            "Layers": [
                "sha256:428c97da766c4c13b19088a471de6b622b038f3ae8efa10ec5a37d6d31a2df0b"
            ]
        },
        "Metadata": {
            "LastTagTime": "0001-01-01T00:00:00Z"
        }
    }
]

Docker "Hello World" Example

Pre-requisite

Running Hello World Example

Explanation

Did you Know?

Docker "Hello World" Example

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