PODS are the atomic unit of scheduling in K8sDocker manages container – VMware manages VM & K8s manages PODsIt is our application or the serviceIt is the basic unit of workNo pod is ever redeployed(Ephemeral) (ie, we can’t get the same pod again. We can get the similar pod.)Pod is running as long the container inside is running.Pods contains one or more containers, at least one.Kubelet will instantiate pods.Pod is running as long the container inside is running.Pods will communicate

The components of K8s worker node are1. kubelet – Kublet is the main K8s agent. It instantiate the pods in the node(only instantiate not create). It helps to register nodes with cluster. Its always watch the api server.It decides who is the master.10255 is the endpoint.2. kube-proxy – Its support for K8s networking. It assigns the ip address for the pods. Each pods inside a node will have same ip address. Load balances across all pods in a service. kube-proxy

Kubernetes master is the in charge of the cluster. Kuberenetes master should be of linux 64 based. The K8’s master have 4 components. They are1. api-server- Server of API’s. It contains all the APIs provided by K8s. It act as the front-end to the control panel, we access via REST API. Similar to ears in human body, it receive the requests2. cluster store – All the requests / data stored in cluster store. etcd is the storage unit use by

Docker is having the scalability challenges and K8s can manage that Docker brings challenges on network, K8s solves that K8s is the container orchestrator tool Auto heal of containers – K8s is self/auto healing K8s runs many containers as a cluster K8s provide the desired state Auto scaling Automatic rollback Load balancing K8s can absorb changes quickly Workload placement Speed of deployment is high Infrastructure abstraction

overlay2 Overlay2 is the preferred storage driver for all currently supported Linux distributions, and requires no extra configurations. fuse-overlayfs Preferred only for running Rootless Docker on a host that does not provide support for rootless overlay2 btrfs and zfs Allows for advanced options, such as creating “snapshots”, but require more maintenance and setup. Each of these relies on the backing filesystem being configured correctly. vfsThe vfs is intended for testing purposes, and for situations where no copy-on-write filesystem can be used. Performance of this

FROMSpecifies the base image. Specified docker image will be downloaded from registry if locally not available.Eg: FROM ubuntu MAINTAINERSpecifies the meta data about the user who creates. LABELSpecifies meta data about the image. It will be in key value pair format Eg: LABEL “Application_Environment”=”Development” LABEL “Application_Support”=”LearnITGuide.net Group” EXPOSEExpose instruction is used to inform about the network port the container listens on runtime. Eg: EXPOSE 80 443 EXPOSE 80/tcp 8080/udp ADDThe instruction helps to copy files, directories and remote URL files

What is Docker Images and Explain in 10 bullet lines? Collection of file systems One copy of docker image get attached to each container. From one image multiple containers can be created Layered structure Each layer is each File system Layer 0 should be base image or Root FS Once image is attached to container, these layers will be attached to the container as a single layer The layers in image will be on read only format, and to have

Create one Image which have base as centos and with git – ntp – httpd.

Create one Image which have base as ubuntu and with git – ntp – apache2

What is the use of “docker update” commands? with example and image Docker update The update command helps to dynamically update the configuration of one or more containers.Update command can be use for prevent containers from consuming too many resources from their Docker hostIt is not supported for windows containers

What is the use of “docker wait” commands? with example and image Docker wait Blocks until one or more containers stop, then print their exit codes. How to check:Start a container in the backgrounddocker run –name abhi httpdRun docker waitdocker wait abhiKill the container from duplicat terminal and check the return value in actual terminaldocker stop abhi

Q1. Explain What is Docker Container with image? Docker container image is the lightweight independent runtime app run time environment.  As said, it contains everything needed to run application. Container is the collection of an user attached to 1 root FS 1 Network & 1 PID. Creation of user session, root file system, network, pid etc will be done by kernel using namespaces. Docker software will directly talk to kernel for this purpose inorder to bypass OS restriction(PC architecture).

3. What is the difference between docker pause and docker unpause? Pause and Unpause are the basic commands in docker.1. pause Pause all processes within one or more containers Eg: docker pause abhi abhi1 2. unpause Unpause all processes within one or more containers Eg: docker unpause abhi abhi1

2. What is the difference between docker stop and docker kill? Docker stop / kill commands are used to stop the running docker container. After docker stop <name>, “docker ps -a ” will show the status as Exited (0) But after docker kill <name>, “docker ps -a ” will show the status as Exited (137).ie, docker stop sends SIGTERM as process end signal and SIGKILL is send by docker kill. root@ip-172-31-28-155:/home/ubuntu# docker start abhiabhiroot@ip-172-31-28-155:/home/ubuntu# docker ps -a | grep abhi2d0eb09c5f08