• Helps manage large clusters
• Load balancing
• Service discovery
• Self monitoring
• Security
• Storage services
• Automated rollbacks
• Optimum resource utilization
• Auto scalable
• Predictable
  

What are the components of Kubernetes master and explain each component’s function?
API Server
-All requests come to API server. REST based.
etcd
-storage for cluster configuration and state
Controller
-keeps tracks of the pods and reports to API server
Scheduler
-assigns a pod to a node based on resource requirements

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

kubelet
-gets requests from scheduler and manages pods based on that.
kube-proxy
-handles all networking in a node, managing pod IPs.
Container runtime
-responsible for running containers

What is Pod in kubernetes. Exaplin in 15 points with image as an example
A Pod is the smallest deployable unit
Contains one or more containers
Each Pod has a unique IP
All containers running in a Pod share the same IP
Pods are instantiated
A Pod is not a process, but an environment for running containers

Q2. Build all these 5 images and run container and observe the use cases of it.
https://devopsschool.com/tutorial/docker/dockerfile/dockerfile-example-sample-lab.html

Q3. Write a example dockerfile with 2 CMD, 2 ENTRYPOINT and 1 CMD/1ENTRYPOINT and write down a behavior of it.
if ENTRYPOINT is not specified, default is /bin/sh, what is specified in CMD is passed as args.
2 CMD -> last one is executed
CMD echo “Hello world1”
CMD echo “Hello world2”
Output: Hello world2

2 ENTRYPOINT -> last one is executed
ENTRYPOINT [“/bin/echo”, “Hello1”]
ENTRYPOINT [“/bin/echo”, “Hello2”]
Output: Hello2

1 CMD/ 1 ENTRYPOINT
CMD echo “Hello world”
ENTRYPOINT [“/bin/echo”, “Hello2”]
Output: Hello2 /bin/sh -c echo “Hello world”

List out number of storage/volume drivers supported by docker?
Volume driver allows to abstract the underlying storage system. The storage can be local, network or cloud.
Volume driver plugins example:
Azure File Storage Plugin
VMware vSphere Storage Plugin
Netshare plugin
OpenStorage plugin

What is Docker Images and Explain 10 bullet lines?
A docker image contains all the dependencies needed to run an application
It is created as layers of file system on top of each other
Layering help update easy and efficient
When conflict happens, topmost layer gets precedence.
Any no.of containers can be created out of a single image
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Create one Image which have base as centos and with git – ntp – httpd

used chrony instead of ntp
root@ip-172-31-28-155:/home/ubuntu# docker run -itd centos
793a59b5cbbebb3af8d373c20b28161cfca60e050a282a455b4349bdadb45315

docker attach 793a59b5cbbe
yum install git
yum install chrony
yum install httpd
docker commit -m”cent-git-chrony-httpd” 793a59b5cbbe cent-git-chrony-http

cent-git-chrony-http latest 62682df1872f 10 minutes ago 372MB

Create one Image which have base as ubuntu and with git – ntp – apache2.
root@ip-172-31-28-155:/home/ubuntu# docker run -itd ubuntu
254f2f37b7a7f7656d9595f2277c0ecefcf25ea9fcf3b1440055ec45b07a19fd

docker attach 254f2f37b7a7
apt-get update
apt-get install git
apt-get install ntp
apt-get install apache2
docker commit -m”ubu-git-ntp-apa” 254f2f37b7a7 ubu-git-ntp-apa

ubu-git-ntp-apa latest 43175557dca4 About a minute ago 259MB

root@ip-172-31-28-155:/home/ubuntu# docker run -itd ubu-git-ntp-apa
4c7c73feedd35567edef71c35d7ad7ce42d843a0d92aa5045364607d75614f95

root@ip-172-31-28-155:/home/ubuntu# docker exec 4c7c73feedd3 git
usage: git [–version] [–help] [-C ] [-c =]

• “docker update” is used to limit the usage of resources a container can use.
• CPU usage can be limited by CPU time, no.of CPUs used, or which CPUs are used.
• Memory usage can be limited for Main Memory as well as Swap
• Disk IO can be limited by specifying a relative weight.
• No.of PIDs container can allocate can be limited.
• This command can also be used to specify the restart policy when container exits.

Q2. – What is the use of “docker wait” commands? with example and image
“docker wait” waits till the container exits and then prints its exit code.
The exit code indicates what was returned by the parent process (PID 1) in the container.
In success case, exit code is 0.

Q3. – List of Top 5 docker images from hub.docker.com and create a running container of it and try to use it
nginx, alpine, python, httpd, rabbitmq

Q2. What is the differenece between docker stop and docker kill?
Docker stop is gracefully stopping a container, first SIGTEM is sent for cleanup and then SIGKILL
Docker kill is forcefully terminating a container directly sending SIGKILL

Q3. What is the difference between docker pause and docker unpause?
Docker pause pauses the execution of container, suspends all processes
Docker unpuase resumes the execution of all processes