Debug School: Asit sahoo

The list of resources which We learnt in this session with 1 liner explanation.

Asit sahoo — Fri, 11 Nov 2022 05:52:38 +0000

Replication controller : It means number of pod replicas running at any one time .
Deployment : It runs multiple replicas of the application and automatically replaces if any instance got failed, it ensures that one or more instance of your application is available.
Labels : It's a key value pair which identifies that are attached to objects such as pods.
Services : It works as a Load balancer.
CLuster Ip : LoadBalance POD and Only accessible inside
cluster
nodeport : Create clusterip svc , It would port-forward at
each node of the cluster
loadbalancer : create LB and add each worker to LB.
Persistent Volume / PVC : PV means storage of cluster given by storage Administrator . PVC means we can claim the storage from PV and mount it to pod, containers.
Configmap and Secrets : Configmap used to store configuration of files , commandline arguments, environemnt files.

Secret used to store data in base 64 encoding format ,
passwords, token.

Stateful set : It's always be in sequential order when ever we create a pod like pod1--pod2 -- pod3
Daemon set : It's a agent used in each machine or VM. We normally used like one POD in each worker for better monitoring purpose , maintenance activity , security concerns.
Cron Job : It creates jobs on repeating schedule like in a crontab file.

What is POD?

Asit sahoo — Wed, 09 Nov 2022 07:49:35 +0000

It's a unit scheduling which contains containers inside pod.
pods have multiple containers.
tight coupling.
Pod contains multi containers and with the resource allocation things.
Pod is a deployable objects in kubernetes.

How Kubernetes works?

Asit sahoo — Wed, 09 Nov 2022 07:46:24 +0000

Kubernetes has the master and worker nodes .

Matser Nodes:

Api Server which exposes the API(REST) consumes Json via manifets files.
Cluster store which works as a storage names etcd kept data as key value pairs.
kube control manager , node contoller, end point controller watches changes in any of pods in desired state.
Kube scheduler check if any ne pods need to instantiate and communicate with APi server.

Worker nodes:

container engine means pulling images, starting/stopping container.
kubelet watches api server, instantiate pods , exposes end points(10255)
kube proxy it contains pod ip addresses, load balance across all services in pod. 3.

Why we need Kubernetes?

Asit sahoo — Wed, 09 Nov 2022 07:16:59 +0000

Containers bring scalability challenges.
Self healing.
Storage orchestration.
Automatically deployment purpose.
Load balancing.
Easy way to scale your application comparing to virtual machines.
deploying images and containers.

What is kubernetes ?

Asit sahoo — Wed, 09 Nov 2022 07:09:11 +0000

It is container Orchestrator.
Improve the scalability things.
Workload management .
Automating software deployments, scaling and management.
Desired state.
Ability to recover quickly.
Ability to do the changes required whenever needed.
Speed of deployment.
Ability to hide the complexity in the cluster.

Diff between docker stop and docker kill?

Asit sahoo — Tue, 08 Nov 2022 05:04:27 +0000

Docker stop command stops the container gracefully but if the docker stop command failed to terminate within the specified time Docker kill command forcefully terminate it.

The docker kill command terminates the process abruptly.

Diff between docker pause and docker unpause?

Asit sahoo — Tue, 08 Nov 2022 04:55:59 +0000

docker pause 6157a3fe61aa
48 docker run httpd
49 docker pause asit
50 docker start asit
51 docker ps -a
52 docker pause 7ca9f93eb310
53 docker pause asit
54 docker stats asit
55 docker unpause asit
56 docker stats asit
57 docker ps
CONTAINER ID NAME CPU % MEM USAGE / LIMIT MEM % NET I/O BLOCK I/O PIDS
34bc638e7336 keen_keller 0.01% 8.785MiB / 3.701GiB 0.23% 656B / 0B 0B / 0B 82

Difference will be CPU will not be allocated while running docker pause and when we do unpause in CPU allocation will start.