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moby--moby/docs/sources/examples/hello_world_daemon.rst

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:title: Hello world daemon example
:description: A simple hello world daemon example with Docker
:keywords: docker, example, hello world, daemon
.. _hello_world_daemon:
Hello World Daemon
==================
.. include:: example_header.inc
The most boring daemon ever written.
This example assumes you have Docker installed and with the base image already imported ``docker pull base``.
We will use the base 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=$(docker run -d base /bin/sh -c "while true; do echo hello world; sleep 1; done")
We are going to run a simple hello world daemon in a new container made from the base image.
- **"docker run -d "** run a command in a new container. We pass "-d" so it runs as a daemon.
- **"base"** is the image we want to run the command inside of.
- **"/bin/sh -c"** is the command we want to run in the container
- **"while true; do echo hello world; sleep 1; done"** is the mini script we want to run, that will just print hello world once a second until we stop it.
- **$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
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
docker attach $CONTAINER_ID
Attach to the container to see the results in realtime.
- **"docker attach**" This will allow us to attach to a background process to see what is going on.
- **$CONTAINER_ID** The Id of the container we want to attach too.
.. code-block:: bash
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
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
docker ps
Make sure it is really stopped.
**Video:**
See the example in action
.. raw:: html
<div style="margin-top:10px;">
<iframe width="560" height="350" src="http://ascii.io/a/2562/raw" frameborder="0"></iframe>
</div>
Continue to the :ref:`python_web_app` example.