DEV Community: sravya-07

Kubernetes - Part 2 - Replicas and Deployments?

sravya-07 — Mon, 21 Nov 2022 21:18:01 +0000

Replicas & ReplicaSets

A replica is a nothing more than a copy. If you have your application hosted on a pod, and you want more instances of the application to be up to serve increased traffic, you can create more replicas of the pod.
As the name suggests, all replicas of a pod are identical to each other
Replicas of a pod are managed using replica sets
A replica set is used to maintain a fixed number of copies of a pod in the Kubernetes cluster
The pods that are managed by the replica set are selected using "selectors"
Any pod that is selected by the selector of a replica set will now be managed by the replica set
Pods will be deleted or created to match the number of replicas specified the yaml file or the cli command

Deployments

Deployments are a way to manage stateless applications hosted on pods/replica sets
They are great for scaling up/down stateless applications
Deployments provide way to perform upgrades. Eg: If you want to change the underlying image in the pod, you can use various update techniques to achieve that

Kubernetes - Part 1 - What are Pods in Kubernetes ?

sravya-07 — Thu, 13 Oct 2022 05:13:33 +0000

Pods are the most basic and the smallest unit in Kubernetes. A pod is a grouping of one or more containers.
The container is created using a Docker image. This image can be pulled from public or private repositories.
All the containers in a pod have shared resources. Pods are a Kubernetes abstraction over containers.

In Kubernetes, we rarely work with containers, and we are mainly working with the pod that is running the container. The pod is what is the host for the application.

In order to view all the pods that running in a k8s cluster, the following commands can be used
kubectl get pods # show pods in default namespace kubectl get pods -n namespace-name # show pods in a particular namespace kubectl get pods -A # show pods in all namespaces kubectl get pods --all-namespaces # show pods in all namespaces

How to resolve python command not found error in Linux

sravya-07 — Fri, 17 Jun 2022 19:03:13 +0000

I had both python3.8 and python2.7 installed on a Linux system (Ubuntu in this case, but this solution should work for other flavours of Linux too), however running python --version gave a python: command not found response.

Steps to resolve:

Verify if any version of python was installed on the system
- I wanted to be sure that the system had some version of python installed. Using whereis python3 or whereis python2 command shows the versions and paths of python installed on the system. The output should look something like this
If there is no version of python installed, install it using sudo apt-get install python3.8 or sudo apt-get install python<version> (use yum instead of apt-get for RHEL)
cd to /usr/bin folder and create a symlink to the version of python you want to be invoked using the python command.
Example:
cd /usr/bin ln -s /usr/bin/python3.8 python
Verify the if the symlink is created using ls -l python and verify if the python command works and is pointing to the right version of python using python --version.