:title: Hello world example :description: A simple hello world example with Docker :keywords: docker, example, hello world .. _running_examples: Check your Docker install ------------------------- This guide assumes you have a working installation of Docker. To check your Docker install, run the following command: .. code-block:: bash # Check that you have a working install $ sudo docker info If you get ``docker: command not found`` or something like ``/var/lib/docker/repositories: permission denied`` you may have an incomplete Docker installation or insufficient privileges to access docker on your machine. Please refer to :ref:`installation_list` for installation instructions. .. _hello_world: Hello World ----------- .. include:: example_header.inc This is the most basic example available for using Docker. Download the small base image named ``busybox``: .. code-block:: bash # Download a busybox image $ sudo docker pull busybox The ``busybox`` image is a minimal Linux system. You can do the same with any number of other images, such as ``debian``, ``ubuntu`` or ``centos``. The images can be found and retrieved using the `Docker index`_. .. _Docker index: http://index.docker.io .. code-block:: bash $ sudo docker run busybox /bin/echo hello world This command will run a simple ``echo`` command, that will echo ``hello world`` back to the console over standard out. **Explanation:** - **"sudo"** execute the following commands as user *root* - **"docker run"** run a command in a new container - **"busybox"** is the image we are running the command in. - **"/bin/echo"** is the command we want to run in the container - **"hello world"** is the input for the echo command **Video:** See the example in action .. raw:: html ---- .. _hello_world_daemon: Hello World Daemon ------------------ .. include:: example_header.inc And now for the most boring daemon ever written! We will use the Ubuntu image to run a simple hello world daemon that will just print hello world to standard out every second. It will continue to do this until we stop it. **Steps:** .. code-block:: bash container_id=$(sudo docker run -d ubuntu /bin/sh -c "while true; do echo hello world; sleep 1; done") We are going to run a simple hello world daemon in a new container made from the ``ubuntu`` image. - **"sudo docker run -d "** run a command in a new container. We pass "-d" so it runs as a daemon. - **"ubuntu"** is the image we want to run the command inside of. - **"/bin/sh -c"** is the command we want to run in the container - **"while true; do echo hello world; sleep 1; done"** is the mini script we want to run, that will just print hello world once a second until we stop it. - **$container_id** the output of the run command will return a container id, we can use in future commands to see what is going on with this process. .. code-block:: bash sudo docker logs $container_id Check the logs make sure it is working correctly. - **"docker logs**" This will return the logs for a container - **$container_id** The Id of the container we want the logs for. .. code-block:: bash sudo docker attach --sig-proxy=false $container_id Attach to the container to see the results in real-time. - **"docker attach**" This will allow us to attach to a background process to see what is going on. - **"--sig-proxy=false"** Do not forward signals to the container; allows us to exit the attachment using Control-C without stopping the container. - **$container_id** The Id of the container we want to attach too. Exit from the container attachment by pressing Control-C. .. code-block:: bash sudo docker ps Check the process list to make sure it is running. - **"docker ps"** this shows all running process managed by docker .. code-block:: bash sudo docker stop $container_id Stop the container, since we don't need it anymore. - **"docker stop"** This stops a container - **$container_id** The Id of the container we want to stop. .. code-block:: bash sudo docker ps Make sure it is really stopped. **Video:** See the example in action .. raw:: html The next example in the series is a :ref:`nodejs_web_app` example, or you could skip to any of the other examples: * :ref:`nodejs_web_app` * :ref:`running_redis_service` * :ref:`running_ssh_service` * :ref:`running_couchdb_service` * :ref:`postgresql_service` * :ref:`mongodb_image` * :ref:`python_web_app`