Debug School: VarunPuligilla1008

Namespaces, PODs, Replicasets and Deployment

VarunPuligilla1008 — Tue, 17 Oct 2023 12:13:42 +0000

Namespaces

Namespaces creates a logical separation in a cluster. Namespaces are used to create kubernetes resources like pods, replica sets and deployments.

Pods

Pods in kubernetes cluster are created using a markup language called yaml. A user can perform CRUD Operations on kubernetes resources.
With the following list of commands a user can do troubleshooting:
Troubleshooting and Debugging Commands:
describe Show details of a specific resource or group of resources
logs Print the logs for a container in a pod
attach Attach to a running container
exec Execute a command in a container
port-forward Forward one or more local ports to a pod
proxy Run a proxy to the Kubernetes API server
cp Copy files and directories to and from containers
auth Inspect authorization
debug Create debugging sessions for troubleshooting workloads and nodes

ReplicaSets or ReplicaController

ReplicaSets or ReplicaControllers are used to create 'n' number of instances based on need in a cluster. The instances can be scaled up or down too.

Deployment

Deployments are used to enable versioning, Upgrades and Rollback along with controlling the replicas.

POD by Varun

VarunPuligilla1008 — Mon, 16 Oct 2023 11:56:54 +0000

What is POD??

A POD is an atomic unit of scheduling in kubernetes. PODs are used to run containers within it and which in turn brings up the applications. kubernetes contains static pods and cluster managed pods. cluster managed pods are monitored by controller manager and it ensures that the pods are always in desired state. Pods are always initialized but never created. The state pod the pod is always decided based on the status of the container within it. A pod can contain two containers within it. first one is primary and second container is called as side car. To create a pod, the user will have to use a declarative language yaml. Whenever, a yaml file is passed via kubectl, it gets converted to a json file and then send to kube-api server. The api-server will validate the kind value and then create a pod. Pods are associated with an IP.

Kubernetes Introduction by Varun

VarunPuligilla1008 — Mon, 16 Oct 2023 07:29:02 +0000

What is Kubernetes?

Kubernetes is a container orchestration technology founded by google. In 2015, It was made open source and currently being managed by CNCF Foundation.

Why Do we need Kubernetes? Explain in 10 lines

We will need kubernetes to manage our applications that are deployed in production environments. Kubernetes can be configured on physical hardware server as well as on a Virtual Machine.
Kubernetes provide us many capabilities in terms of scalability, high availability, auto scaling, load balancing incoming traffic, seamless upgrades and rollbacks.

How Kubernetes Works?

Kubernetes works in master and slave model. All the containerized applications are deployed as a pod in a slave node. slave node a.k.a, worker node, minion etc., A master node can manage any number of worker nodes provided they have to be associated with master. A worker node can be registered or associated to a master node by using it's certificate. Once the worker node is associated, then the master node will start delegating tasks to worker node.

Kubernetes Architectecture. Explain each component with one line.

Kubernetes Architecture consists of Master and worker node.
A node is tagged as a master node when it is configured with 4 components namely, kube-api server, controller manager, etcd & scheduler.
A node is tagged as a worker node when it is configured with 3 components namely, kubelet, kube-proxy and container runtime.

Kube API server is a component that contains 100's of APIs and is used to talk to worker nodes and the components within the entire cluster. API Server listens on port 6443

controller manager is a component that will take care of lifecycle of cluster. It is will monitor the health status of pods, nodes and ensure that the cluster is always in desired state.

Scheduler is a components that delegates the tasks or jobs to worker nodes based on the configured constraints.

etcd is a key:value based cluster storage that manages all the secrets,
certificate etc., within the cluster.

Kubelet is a kubernetes agent that is installed on a worker node and is used to interact with kube-api server to do jobs.

Kube-proxy is a component installed in worker node that takes care of assigning IPs and traffic routing within the nodes.

container engine is a component installed in worker node that take care of running containers.