Kubernetes

How To Use Issue Commands to the OpenStack and Magnum Servers

There are three ways of working with Kubernetes clusters within Openstack Magnum and Horizon modules:

Horizon Commands

You issue Horizon commands using mouse and keyboard, through predefined screen wizards. It is the easiest way to start but not the most productive in the long run.

Command Line Interface (CLI)

CLI commands are issued from desktop computer or server in the cloud. This approach allows you to save commands as text and repeat them afterwards. This is the preferred way for professionals.

HTTPS Requests to the Magnum Server

Both the Horizon and the CLI use HTTPS requests internally and in an interactive manner. You can, however, write your own software to automate and/or change the state of the server, in real time.

What We Are Going To Cover

• How to install the CLI – OpenStack and Magnum clients

• How to connect the CLI to the Horizon server

• Basic examples of using OpenStack and Magnum clients

Notes On Python Versions and Environments for Installation

OpenStack is written in Python so you need to first install a Python working environment and then install the OpenStack clients. Officially, OpenStack runs only on Python 2.7 but you will most likely only be able to install a version 3.x of Python. During the installation, adjust accordingly the numbers of Python versions mentioned in the documentation.

You will be able to install Python on any of the popular platforms, such as Windows, MacOS, Linux on a desktop computer. Or, supposing you are logged into Horizon interface, you can use commands Compute => Instances to create an instance of a virtual machine. Then install the Python there. Ubuntu 18.04 or 20.04 would serve best in this regard.

You can install the Python and the clients on several environments at once, say, on a desktop computer and on a virtual machine on the server, at the same time. Following the instructions in this tutorial, they will all be connected to one and the same Kubernetes cluster anyway.

Prerequisites

No. 1 Hosting

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

No. 2 Installation of OpenStack CLI on Ubuntu 18.04 Server

The article How to install OpenStackClient (Linux)? shows how to install OpenStack client on Ubuntu server. That Ubuntu may be the desktop operating system, a virtual machine on some other operating system, or an Ubuntu server in the cloud.

Installation on Mac OS will be similar to the installation on Ubuntu.

No. 3 Installation of OpenStack CLI on Windows

The article How to install OpenStackClient (Windows)? GitBash/Cygwin shows the installation on Windows.

No. 4 General Instructions for Installation of OpenStack Clients

There are various ways of installing Python and the required clients. For instance, on MacOS, you can install the clients using Python PIP or install them natively, using homebrew.

The article Install the OpenStack command-line clients will give a systematic introduction to installation of OpenStack family of clients on various operating systems.

Once installed, the CLI commands will be identical across various platforms and operating systems.

No. 5 Create Python 3 Virtual Environment

Create Python 3 virtual environment using the venv module with this command:

python3 -m venv py3-sphinx

Now “activate” the environment, which is here called py3-sphinx:

source py3-sphinx/bin/activate

The command prompt in terminal will start out with the name of the environment:

(py3-sphinx) $

On MacOS, under which these documents have been written, the command prompt might include the name of the user and the directory, for example:

(py3-sphinx) duskosavic@Duskos-iMac CloudFerroDocs %

Step 1 Install the CLI for Kubernetes on OpenStack Magnum

In this step, you are going to install clients for commands openstack and coe, from modules OpenStack and Magnum, respectively.

Follow the Prerequisites Nos. 2, 3 or 4 to install the main client for OpenStack. Its name is python-openstackclient and the installation described in those will typically contain a command such as

pip install python-openstackclient

At the end of installation from either of the prerequisite articles, install Magnum client by issuing this command:

pip install python-magnumclient

Step 2 Connect OpenStack and Magnum Clients to Horizon Cloud

After installation, clients for OpenStack and Magnum are ready to execute on the computer or server. The next step is connecting them to server, through a series of HTTPS calls. First you

• download a token from server, then

• install it on the server or computer where the clients are and then

• use the token in each and every API call to the cloud.

Download OpenStack RC File

From the main menu in Horizon interface execute command API Access and see a screen similar to this:

Some links will have additional parameters in their parameter lists, however, these are erased for security from the image above.

The clients will use the link called Identity

https://keystone.cloudferro.com:5000

for authorization of access.

Click on button Download OpenStack RC File on the right side of the window, then click on menu option OpenStack RC File and download the RC file.

The name of the file to download starts with your username for the Horizon cloud and ends up with openrc.sh. In this case, it will be cloud_00341_1-openrc.sh.

When downloaded, the file will look like this:

Its purpose is to install system variables which the OpenStack and Magnum clients will use to connect to the cloud. The lines that start with export will store a value into a system variable.

Taken together, the information in this file will be sufficient for clients to connect to the cloud.

Execute the RC file with a system app

On Linux systems, files that have an extension .sh are executable files and the first line in the file directs with which application to execute such file. In this case, the first line points to bash, which is a standard shell script under Ubuntu.

Using bash, the command to execute a script on Ubuntu is source:

source ./cloud_00341_1-openrc.sh

Other operating systems will have their own versions of the bash. Under MacOS Big Sur, for example, you would use zsh, like this:

zsh ./cloud_00341_1-openrc.sh

You have to execute this file at the start of every terminal session and it will last until the terminal window is closed. When asked, enter your Horizon password:

Once the password is entered, the password will be exported to a system variable, and the clients will be set up.

Step 3 How to Use the OpenStack Client

In this step, you are going to start using the OpenStack client you have installed and connected to the cloud.

There are two ways of using the OpenStackClient. If you enter the word openstack at the command prompt of the terminal, you will enter the special command line interface, like this:

The benefit would be that you do not have to type openstack keyword for every command.

Type quit to leave the openstack internal command line prompt.

The preferred way, however, is typing the keyword openstack, followed by parameters and running from terminal command line.

Openstack commands may have dozens of parameters so it is better to compose the command in an independent text editor and then copy and paste it into the terminal.

The Help Command

To learn about the available commands and their parameters, type –help after the command. If applied to the keyword openstack itself, it will write out a very long list of commands, which may come useful as an orientation. It may start out like this:

This is how it ends:

The colon in the last line means that the output is in vi (or vim) editor. To leave it, type letter q and press Enter on the keyboard.

Prerequisites No. 3 and 4 lead to official OpenStack user documentation.

Here is what happens when you enter a wrong parameter, say, networks instead of network:

openstack networks list

You get a list of commands similar to what you just typed.

To list networks available in the system, use a singular version of the command:

openstack network list

Step 4 How to Use the Magnum Client

OpensStack command for the server is openstack but for Magnum, the command is not magnum as one would expect, but coe, for container orchestration engine. Therefore, the commands for clusters will always start with openstack coe.

See cluster commands by entering

openstack coe

into the command line:

You can see the existing clusters using the following command:

openstack coe cluster list

This is more or less the same information that you can get from the Horizon interface:

after clicking on Container Infra => Clusters.

Prerequisite No. 5 offers more technical info about the Magnum client.

What To Do Next

In this tutorial you have

• installed the OpenStack and Magnum clients

• connected them to the server, then used

• openstack command to access the server in general and

• coe to access the clusters in particular.

The article How To Use Command Line Interface for Kubernetes Clusters On Creodias OpenStack Magnum explains

• the advantages of using the CLI instead of Horizon interface, showing

• how to create a cluster template as well as

• how to create a new cluster

all via the CLI.