Minimal CoreOS Setup

Goal

  • You will learn how to start a minimal CoreOS instance on the SysEleven Stack.
  • A simple docker container (nginx server) will run on the instance.
  • You will learn how to upload the current CoreOS stable image.

Prerequisites

Clone the example repository

You will be working with the heat examples repository on Github. Your first step is to clone it:

git clone https://github.com/syseleven/heat-examples
cd heat-examples/coreOS

Upload the CoreOS image

We created a helper script in the coreOS example for this example to upload the official stable CoreOS image to the SysEleven Stack.

./upload_replacing_coreos_image.sh

This helper script first downloads the image, deletes existing images on your SysEleven Stack named private_coreos and finally uploads the new image.

The image will reside in the private scope of your project and will persist when the stack is deleted.

Start the CoreOS instances

After uploading the CoreOS image, you can create the stack:

openstack stack create -t cluster.yaml <stack name> --parameter key_name=<ssh key name> --wait

In this command, key_name references an SSH-Key that you created in the SSH Tutorial.
You can start more than one instance setting the optional parameter number_instances. If you do not specify this parameter, only one instance will start up.

Conclusion

You have now started one or more CoreOS instances on the SysEleven Stack. You will be able to access each one using a public floating IP address.

  • openstack server list prints a list of all instances, as well as the corresponding IP addresses.

  • Every CoreOS instance runs a docker container launching an NGINX based web server, listening on port 80. You can check that using the following command: curl <ip-address> (It should only show the nginx welcome page).

  • Connecting to the SSH service is allowed by the security group (defined in the yaml files) as well. You can log in via: ssh core@<ip-address>.

You can change the number of instances on demand. To scale from the current number of instances (default is 1) to 5, you can run this simple command:

openstack stack update -t cluster.yaml <stack name> --parameter key_name=<ssh key name> --number_instances=5 --wait

This setup is still missing a couple pieces to provide load balancing or high availability. Check out the links in the next section for some advanced setups you can build based on this tutorial.

Links/Examples