Kubernetes

How To Access Kubernetes Cluster Post Deployment Using Kubectl On Creodias OpenStack Magnum

Note

This article assumes that you have access to CloudFerro WAW3-1 infrastructure, which has Kubernetes support built-in (OpenStack Magnum module).

If your CREODIAS account has access only to CF2 infrastructure, please contact support to get access to WAW3-1.

In this tutorial, you start with a freshly installed Kubernetes cluster on Cloudferro OpenStack server and connect the main Kubernetes tool, kubectl, to the cloud.

What We Are Going To Cover

How to connect kubectl to the OpenStack Magnum server

How to access clusters with kubectl

Prerequisites

No. 1 Hosting

To follow this article, use your Creodias hosting account with WAW3-1 server and Horizon interface.

No. 2 Installation of kubectl

Standard types of kubectl installation are described on Install Tools page of the official Kubernetes site.

No. 3 A cluster already installed on Magnum site

With Horizon interface: How to Create a Kubernetes Cluster Using Creodias OpenStack Magnum.
With command line interface: How To Use Command Line Interface for Kubernetes Clusters On Creodias OpenStack Magnum.

Or, you may want to create a new cluster called k8s-cluster, just for this occasion – by using the following CLI command:

openstack coe cluster create
   --cluster-template k8s-stable-1.21.5
   --labels eodata_access_enabled=false,floating-ip-enabled=true,master-lb-enabled=true
   --merge-labels
   --keypair sshkey
   --master-count 3
   --node-count 2
   --master-flavor eo1.large
   --flavor eo1.large
   k8s-cluster

Warning

It takes some 10-20 minutes for the new cluster to form.

In the rest of this text we shall use cluster name k8s-cluster – be sure to use the name of the existing cluster instead.

No. 4 Connect openstack client to the cloud

Prepare openstack and magnum clients by executing Step 2 Connect OpenStack and Magnum Clients to Horizon Cloud from article How To Install OpenStack and Magnum Clients for Command Line Interface to Creodias Horizon.

The Plan

Follow up the steps listed in Prerequisite No. 2 and install kubectl on the platform of your choice.

Use the existing Kubernetes cluster on Cloudferro or install a new one using the methods outlined in Prerequisites Nos. 3.

Use Step 2 in Prerequisite No. 4 to enable connection of openstack and magnum clients to the cloud.

You are then going to connect kubectl to the Cloud.

Step 1 Download Certificates From the Server

The openstack command to download the corresponding configuration file from Magnum has these input parameters:

 openstack coe cluster config --help
usage: openstack coe cluster config [-h]
   [--dir <dir>] [--force] [--output-certs]
   [--use-certificate] [--use-keystone]
    <cluster>

Get Configuration for a Cluster

positional arguments:
  <cluster>    The name or UUID of cluster to update

optional arguments:
  -h, --help           show this help message and exit
  --dir <dir>  Directory to save the certificate and config files.
  --force              Overwrite files if existing.
  --output-certs       Output certificates in separate files.
  --use-certificate    Use certificate in config files.
  --use-keystone       Use Keystone token in config files.
 

You will use command

openstack coe cluster config

to download the files that kubectl needs for authentication with the server. Create a new directory called k8sdir into which the files will be downloaded:

mkdir k8sdir

Then download the certificates into that folder:

 openstack coe cluster config
   --dir k8sdir
   --force
   --output-certs
   k8s-cluster
 

There will be four files:

 ls k8sdir
ca.pem               cert.pem        config          key.pem
 

Parameter –output-certs produces .pem files, which are X.509 certificates, originally created so that they can be sent via email. File config combines the .pem files and contains all the information needed for kubectl to access the cloud. Using –force overwrites the existing files (if any), so you are guaranteed to work with only the latest versions of the files from server.

The result of this command is shown in the row below:

 export KUBECONFIG=/Users/duskosavic/CloudferroDocs/k8sdir/config
 

Copy this command and paste it into the command line of terminal, then press the Enter key on the keyboard to execute it. System variable KUBECONFIG will be thus initialized and the kubectl command will have access to the config file at all times.

Step 2 Verify That kubectl Has Access to the Cloud

See basic data about the cluster with the following command:

 kubectl get nodes -o wide
 

The result is:

Security groups rules basic data about the cluster

That verifies kubectl has proper access to the cloud.

To see available commands kubectl has, use:

 kubectl --help
 

The listing is too long to reproduce here, but here is how it starts:

kubectl also has a long list of options, which are parameters that can be applied to any command. See them with

kubectl options

What To Do Next

With kubectl operational, you can

deploy apps on the cluster,

access multiple clusters,

create load balancers,

access applications in the cluster using port forwarding,

use Service to access application in a cluster,

list container images in the cluster

use Services, Deployments and all other resources in a Kubernetes cluster.

Kubernetes dashboard is a visual alternative to kubectl. To install it, see Using Dashboard To Access Kubernetes Cluster Post Deployment On Creodias OpenStack Magnum.