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: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
<iframe width="560" height="400" frameborder="0"
sandbox="allow-same-origin allow-scripts"
srcdoc="<body><script type="text/javascript"
src="https://asciinema.org/a/7658.js"
id="asciicast-7658" async></script></body>">
</iframe>
----
.. _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 to.
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
<iframe width="560" height="400" frameborder="0"
sandbox="allow-same-origin allow-scripts"
srcdoc="<body><script type="text/javascript"
src="https://asciinema.org/a/2562.js"
id="asciicast-2562" async></script></body>">
</iframe>
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`
|
