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page_title: Hello world example page_description: A simple hello world example with Docker page_keywords: docker, example, hello world
Check your Docker installation
This guide assumes you have a working installation of Docker. To check your Docker install, run the following command:
# 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 Installation for installation instructions.
Hello World
Note
:
- This example assumes you have Docker running in daemon mode. For more information please see Check your Docker install.
- If you don’t like sudo then see Giving non-root access
This is the most basic example available for using Docker.
Download the small base image named busybox:
# 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.
$ 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
Hello World Daemon
Note
:
- This example assumes you have Docker running in daemon mode. For more information please see Check your Docker install.
- If you don’t like sudo then see Giving non-root access
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:
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.
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.
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.
sudo docker ps
Check the process list to make sure it is running.
- "docker ps" this shows all running process managed by docker
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.
sudo docker ps
Make sure it is really stopped.
Video:
See the example in action
The next example in the series is a Node.js Web App example, or you could skip to any of the other examples: