INTRODUCTION TO KUBERNETES PART 1
What is Kubernetes and why do we need it ?
Before we explain what Kubernetes does, we need to explain what
containers are and why people are using those.
A container is a mini-virtual machine. It is small, as it does not have
device drivers and all the other components of a regular virtual machine.
Docker is by far the most popular container and it is written in Linux.
Microsoft also has added containers to Windows as well, because they
have become so popular.
The best way to illustrate why this is useful and important is to give an
example.
Suppose you want to install the nginx web server on a Linux server. You
have several ways to do that. First, you could install it directly on the
physical server’s OS. But most people use virtual machines now, so
you would probably install it there.
But setting up a virtual machine requires some administrative effort and
cost as well. And machines will be underutilized if you just dedicate it for
just one task, which is how people typically use VMS. It would be better
to load that one machine up with nginx, messaging software, a DNS server,
etc. The people who invented containers thought through these issues and r
easoned that since nginx or any other application just needs some bare
minimum operating system to run, then why not make a stripped down
version of an OS, put nginx inside, and run that. Then you have a
self-contained, machine-agnostic unit that can be installed anywhere.
Now containers are so popular than they threaten to make VMs obsolete,
is what some people say.
Docker Hub
But making the container small is not the only advantage. The container
can be deployed just like a VM template, meaning an application that is
ready to go that requires little or no configuration.
can be deployed just like a VM template, meaning an application that is
ready to go that requires little or no configuration.
public repository. There, people have taken the time to assemble
opensource software configurations that might take someone else hours
or days to put together. People benefit from that because they can install
nginx or even far more complicated items simply by downloading them
from there.
For example, this one line command will down, install, and start Apache
Spark with Jupyter notebooks (iPython):
docker run -d -p 8888:8888 jupyter/all-spark-notebook
As you can see it is running on port 8888. So you could install something
else on another port or even install a second instance of Spark and Jupyter.
WELCOME TO KUBERNETES THE REASON WE USE KUBERNETES
On the Need for Orchestration
Now, there is an inherent problem with containers, just like there is with virtual
machines. That is the need to keep track of them. When public cloud companies bill
you for CPU time or storage then you need to make sure you do not have any o
rphaned machines spinning out there doing nothing. Plus there is the need to
automatically spin up more when a machine needs more memory, CPU, or storage,
as well as shut them down when the load lightens.
machines. That is the need to keep track of them. When public cloud companies bill
you for CPU time or storage then you need to make sure you do not have any o
rphaned machines spinning out there doing nothing. Plus there is the need to
automatically spin up more when a machine needs more memory, CPU, or storage,
as well as shut them down when the load lightens.
Orchestration tackles these problems. This is where Kubernetes comes in.
Kubernetes
Google built Kubernetes and has been using it for 10 years. That it has
been used to run Google’s massive systems for that long is one of its
key selling points. Two years ago Google pushed Kubernetes into open
source.
been used to run Google’s massive systems for that long is one of its
key selling points. Two years ago Google pushed Kubernetes into open
source.
Kubernetes is a cluster and container management tool. It lets you deploy
containers to clusters, meaning a network of virtual machines. It works
with different containers, not just Docker.
containers to clusters, meaning a network of virtual machines. It works
with different containers, not just Docker.
Kubernetes, at its basic level, is a system for running and coordinating containerized applications across a cluster of machines. It is a platform designed to completely manage the life cycle of containerized applications and services using methods that provide predictability, scalability, and high availability.
Kubernetes Basics
The basic idea of Kubernetes is to further abstract machines, storage, and
networks away from their physical implementation. So it is a single
interface to deploy containers to all kinds of clouds, virtual machines, and
physical machines.
networks away from their physical implementation. So it is a single
interface to deploy containers to all kinds of clouds, virtual machines, and
physical machines.
Here are a few of Kubernetes concepts to help understand what it does.
Node
A node is a physical or virtual machine. It is not created by Kubernetes.
You create those with a cloud operating system, like OpenStack or
Amazon EC2, or manually install them. So you need to lay down your
basic infrastructure before you use Kubernetes to deploy your apps.
But from that point it can define virtual networks, storage, etc. For
example, you could use OpenStack Neutron or Romana to define
networks and push those out from Kubernetes.
You create those with a cloud operating system, like OpenStack or
Amazon EC2, or manually install them. So you need to lay down your
basic infrastructure before you use Kubernetes to deploy your apps.
But from that point it can define virtual networks, storage, etc. For
example, you could use OpenStack Neutron or Romana to define
networks and push those out from Kubernetes.
Pods
A pod is a one or more containers that logically go together. Pods run on
nodes. Pods run together as a logical unit. So they have the same shared
content. They all share the share IP address but can reach other other via
localhost. And they can share storage. But they do not need to all run on
the same machine as containers can span more than one machine. One
node can run multiple pods.
nodes. Pods run together as a logical unit. So they have the same shared
content. They all share the share IP address but can reach other other via
localhost. And they can share storage. But they do not need to all run on
the same machine as containers can span more than one machine. One
node can run multiple pods.
Pods are cloud-aware. For example you could spin up two Nginx
instances and assign them a public IP address on the Google Compute
Engine (GCE). To do that you would start the Kubernetes cluster, configure
the connection to GCE, and then type something like:
instances and assign them a public IP address on the Google Compute
Engine (GCE). To do that you would start the Kubernetes cluster, configure
the connection to GCE, and then type something like:
kubectl expose deployment my-nginx –port=80 –type=LoadBalancer
Deployment
A set of pods is a deployment. A deployment ensures that a sufficient
number of pods are running at one time to service the app and shuts
down those pods that are not needed. It can do this by looking at, for
example, CPU utilization.
number of pods are running at one time to service the app and shuts
down those pods that are not needed. It can do this by looking at, for
example, CPU utilization.
Vendor Agnostic
Kubernetes works with many cloud and server products. And the list is
always growing as so many companies are contributing to the open
source project. Even though it was invented by Google, Google is not said
to dominate it’s development.
always growing as so many companies are contributing to the open
source project. Even though it was invented by Google, Google is not said
to dominate it’s development.
To illustrate, the OpenStack process to create block storage is called
Cinder. OpenStack orchestration is called Heat. You can use Heat with
Kubernetes to manage storage with Cinder.
Cinder. OpenStack orchestration is called Heat. You can use Heat with
Kubernetes to manage storage with Cinder.
Kubernetes works with Amazon EC2, Azure Container Service, Rackspace,
GCE, IBM Software, and other clouds. And it works with bare-metal (using
something like CoreOS), Docker, and vSphere. And it works with libvirt
and KVM, which are Linux machines turned into hypervisors (i.e, a
platform to run virtual machines).
GCE, IBM Software, and other clouds. And it works with bare-metal (using
something like CoreOS), Docker, and vSphere. And it works with libvirt
and KVM, which are Linux machines turned into hypervisors (i.e, a
platform to run virtual machines).
Use Cases
So why would you use Kubernetes on, for example, Amazon EC2, when it
has its own tool for orchestration (CloudFormation)? Because with
Kubernetes you can use the same orchestration tool and command-line
interfaces for all your different systems. Amazon CloudFormation only
works with EC2. So with Kubernetes you could push containers to the
Amazon cloud, your in-house virtual and physical machines as well, and
other clouds.
has its own tool for orchestration (CloudFormation)? Because with
Kubernetes you can use the same orchestration tool and command-line
interfaces for all your different systems. Amazon CloudFormation only
works with EC2. So with Kubernetes you could push containers to the
Amazon cloud, your in-house virtual and physical machines as well, and
other clouds.
Wrapping Up
So we have answered the question what is Kubernetes? It is an
orchestration tool for containers. What are containers? They are small
virtual machines that run ready-to-run applications on top of other virtual
machines or any host OS. They greatly simplify deploying applications.
And they make sure machines are fully-utilized. All of this lowers the cost
of cloud subscriptions, further abstracts the data center, and simplifies
operations and architecture. To get started learning about it, the reader
can install MiniKube to run it all on one machine and play around with it.
orchestration tool for containers. What are containers? They are small
virtual machines that run ready-to-run applications on top of other virtual
machines or any host OS. They greatly simplify deploying applications.
And they make sure machines are fully-utilized. All of this lowers the cost
of cloud subscriptions, further abstracts the data center, and simplifies
operations and architecture. To get started learning about it, the reader
can install MiniKube to run it all on one machine and play around with it.
WAIT FOR THE NEXT PART WHERE I WILL TELL YOU MORE ABOUT KUBERNETES AND THE COMMANDS USED IN KUBERNETES
by Sudhanshu arora
email id -sudhanshu.techycardia@gmail.com
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