sarath – Best DevOps

What is Pod in kubernetes. Exaplin in 15 points with image as an example

sarath — Wed, 01 Sep 2021 07:22:01 +0000

atomic unit of scheduling
all container in pod share the pod environment. anything attached to pod, all container can use it.
it can contain one or more containers.
pod can have tight coupling- loose coupling.
pods are atomic, you can scale the port from 1 to many.
pods are the application which can access through n/w.
pods contain container. and runs as long as container run.
multi container pods – main container and side car container.
pod lifecycle: phase: pending –> phase: running –> phase: succeeded/failed.
inter pod communication : using pod n/w (created by kube-proxy).
intra pod communication: through localhost
no pod is ever redeployed
unit of scheduling
remote access: using pod IP address and pod port number(multi container).

What are the components of Kubernetes worker and explain each component’s function?

sarath — Wed, 01 Sep 2021 07:20:54 +0000

kubelet: just like a slave. the main kubernetes agent. register node with cluster- master approves it. watches api server.kubelet will talk to api server with health status.
instantiate pods – not creation. pod is the logical unit of cluster. exposes end points on 10255.
container engine: does container management. ex:docker
kube proxy: it assign pod ip address, all containers in a pod shared a single ip. load balances across all pods in a service.

What are the components of Kubernetes master and explain each component’s function?

sarath — Wed, 01 Sep 2021 07:19:59 +0000

api server: all the feature available at api server. , front end to control plane. anything want to master , can send to api server.
it can be using http, it consumes json file. internally it communicates with each other.
cluster store:any req is send is stored here. internal communication(worker to master etc.) also stored here. it uses etcd (open source) to store.it should exist in etcd- source of truth.
controller manager: collection of controller. node controller(all the monitoring activities), endpoints controller. watches for changes. helps to maintain desired state.
kube scheduler: watches api server for new pods. assign work to neodes.(affinity/anti-affinity)

Write down 10 fearures of Kubernetes with image

sarath — Wed, 01 Sep 2021 07:19:11 +0000

k8s is container orchestration tool
workload placement ,k8s helping infrastructure abstraction
help to manage desired state
self healing, replace with desired state
automatic rollback/rollouts – rollback the feature / version
auto scaling – 5 container to 50 container can be done
load balancing of container/pods
high speed of deployment. upgrade/
ability to rollback
storage orchestration.

List out all INSTRUCTION statement of dockerfile and give one line explanation.

sarath — Tue, 31 Aug 2021 07:31:45 +0000

FROM: The FROM instruction initializes a new build stage and sets the Base Image for subsequent instructions
RUN: The RUN instruction will execute any commands in a new layer on top of the current image and commit the results.
MAINTAINER: The MAINTAINER instruction sets the Author field of the generated images.
EXPOSE: The EXPOSE instruction informs Docker that the container listens on the specified network ports at runtime
ENV: The ENV instruction sets the environment variable to the value
ADD: The ADD instruction copies new files, directories or remote file URLs from and adds them to the filesystem of the image at the path .
ENTRYPOINT: sets PID to 1.
ARG : SET A VARIABLE for DOCKERFILE
WORKDIR : sets working directory
USER : set a container run time user.
VOLUME: creates mount point

What is the use of “docker wait” commands? with example and image

sarath — Mon, 30 Aug 2021 11:33:45 +0000

Block until one or more containers stop, after that it print their exit codes.
root@ip-172-31-28-155:/home/ubuntu# docker wait test_httpd

root@ip-172-31-28-155:/home/ubuntu# docker stop test_httpd
test_httpd

root@ip-172-31-28-155:/home/ubuntu# docker wait test_httpd
0

Assignment for docker day 1

sarath — Mon, 30 Aug 2021 11:25:29 +0000

Q1. – What is the use of “docker update” commands? with example and image

The docker update command dynamically updates container configuration. it prevent containers from consuming too many resources such as CPU and memory from their Docker host.

ex:

$ docker update --cpu-shares 512 container_id

Assignment for docker day 1

sarath — Mon, 30 Aug 2021 07:43:50 +0000

Q> What is the difference between docker pause and docker unpause?
docker pause command suspends all processes in the specified containers and unpause will resume all suspended processes within containers

Assignment for docker day 1

sarath — Mon, 30 Aug 2021 07:42:04 +0000

Q.What is the differenece between docker stop and docker kill?
docker stop attempts to trigger a graceful shutdown by sending the signal SIGTERM, whereas kill just kills the process by default

Assignment for docker day 1

sarath — Mon, 30 Aug 2021 07:37:38 +0000

Q1. Explain What is Docker Container with image?
Docker container image is a lightweight, standalone, application run time environment and from one docker image we can get multiple container.