Install Python 3.6.4 on CentOS 7 From a Repository

Install Python 3.6.4 on CentOS 7 From a Repository

This is the easier method of the two for installing Python on your machine. Here, we simply add a repository that has the pre-compiled version ready for us to install. In this case, we are adding the Inline with Upstream Stable repository, a community project whose goal is to bring new versions of software to RHEL-based systems.

Step 1: Open a Terminal and add the repository to your Yum install.

sudo yum install -y https://centos7.iuscommunity.org/ius-release.rpm

Step 2: Update Yum to finish adding the repository.

sudo yum update

Step 3: Download and install Python.

This will not only install Python – but it will also install pip to help you with installing add-ons.

sudo yum install -y python36u python36u-libs python36u-devel python36u-pip

Once these commands are executed, simply check if the correct version of Python has been installed by executing the following command:

python3.6 -V

You have now finished installing Python 3.6.4 on your CentOS 7 machine, as well as installing a native Python package management tool called pip.

Ansible Ad-Hoc Commands

Syntax
# Command hostgroups module/arguements[options]


Examples
#ansible webserver reboot
#ansible all -a uptime
#ansible all -a "uname -a"
#ansible all -m 
# ansible-doc -l |more
#ansible-doc -l |more |wc -l
#ansible-doc -l | grep -i <modulename>
#ansible-doc <modulename>
#ansible-doc -s <modulename>
example
#ansible all -m ping
#ansible all -m ping -o
#ansible all -m user -a "name=john password=redhat"
#rpm -q httpd
#ansible all -a "yum -y install httpd"
rpm -q httpd
#ansible all -a "yum -y remove httpd"

#ansible all -m yum -a "name=httpd state=present"
#ansible all -m yum -a "name=httpd state=absent"

#ansible all -m shell -a "uname -a;df -h" -v

Installing Ansible on Ubuntu

Installing Ansible
Next, install Ansible. Here are the steps to make that happen:

Log into the Ubuntu Server that will host Ansible
Install the necessary repository with the command sudo apt-add-repository ppa:ansible/ansible.
Update apt with the command sudo apt-get update.
Install Ansible with the command sudo apt-get install ansible -y.
Because Ansible requires a Python interpreter (in order to run its modules), we need to install Python as well. For that, issue the command:

sudo apt-get install python -y
Note: You may find Python already installed.

At this point, Ansible is installed and ready to go.

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split(/:([^:]+)$/, $str)

Top 15 Docker interview questions

Q1. What are the differences between Docker and Hypervisors?
Docker vs Hypervisors Features Hypervisors Docker Default Security Support
To a great degree
To a slightly less degree Memory on disk required
Complete OS plus apps
App requirement only Time Taken to start up
Substantially longer as it requires boot of OS plus app loading
Substantially shorter as apps only need to start as the kernel is already running Portability
Portable with proper preparation
Portable within image format; typically smaller Operating System
Supports multiple OS
It uses the host OS
Q2. What is Docker?
I will suggest you to start with a small definition of Docker.
• Docker is a containerization platform which packages your application and all its dependencies together in the form of containers so as to ensure that your application works seamlessly in any environment be it development or test or production.
• Docker containers, wrap a piece of software in a complete filesystem that contains everything needed to run: code, runtime, system tools, system libraries etc. anything that can be installed on a server.
• This guarantees that the software will always run the same, regardless of its environment.
You can refer the diagram shown below, as you can see that containers run on a single machine share the same operating system kernel, they start instantly as only apps need to start as the kernel is already running and uses less RAM.
Note: Unlike Virtual Machines which has its own OS Docker containers uses the host
OS
Q3. What is Docker image?
I will suggest you to go with the below mentioned flow:
Docker image is the source of Docker container. In other words, Docker images are used to create containers. Images are created with the build command, and they’ll produce a container when started with run. Images are stored in a Docker registry such as registry.hub.docker.com because they can become quite large, images are designed to be composed of layers of other images, allowing a minimal amount of data to be sent when transferring images over the network. Tip: Be aware of Dockerhub in order to answer questions on pre-available images.
Q4. What is Docker container?
This is a very important question so just make sure you don’t deviate from the topic and I will advise you to follow the below mentioned format:
Docker containers include the application and all of its dependencies, but share the kernel with other containers, running as isolated processes in user space on the host operating system. Docker containers are not tied to any specific infrastructure: they run on any computer, on any infrastructure, and in any cloud. Now explain how to create a Docker container, Docker containers can be created by either creating a Docker image and then running it or you can use Docker images that are present on the Dockerhub.
Docker containers are basically runtime instances of Docker images.
Q5 What is Docker hub?
Answer to this question is pretty direct.
Docker hub is a cloud-based registry service which allows you to link to code repositories, build your images and test them, stores manually pushed images, and links to Docker cloud so you can deploy images to your hosts. It provides a centralized resource for container image discovery, distribution and change management, user and team collaboration, and workflow automation throughout the development pipeline.
Q6. How is Docker different from other container technologies?
According to me, below, points should be there in your answer:
Docker containers are easy to deploy in a cloud. It can get more applications running on the same hardware than other technologies, it makes it easy for developers to quickly create, ready-to-run containerized applications and it makes managing and deploying applications much easier. You can even share containers with your applications. If you have some more points to add you can do that but make sure the above the above explanation is there in your answer.
Q7. What is Docker Swarm?
You should start this answer by explaining Docker Swarn.
Docker Swarm is native clustering for Docker. It turns a pool of Docker hosts into a single, virtual Docker host. Docker Swarm serves the standard Docker API, any tool that already
communicates with a Docker daemon can use Swarm to transparently scale to multiple hosts.
I will also suggest you to include some supported tools:
• Dokku
• Docker Compose
• Docker Machine
• Jenkins
Q8. What is Dockerfile used for?
This answer, according to me should begin by explaining the use of Dockerfile.
Docker can build images automatically by reading the instructions from a Dockerfile.
Now I will suggest you to give a small definition of Dockerfle.
A Dockerfile is a text document that contains all the commands a user could call on the command line to assemble an image. Using docker build users can create an automated build that executes several command-line instructions in succession.
Q9. Can I use json instead of yaml for my compose file in Docker?
You can use json instead of yaml for your compose file, to use json file with compose, specify the filename to use for eg: docker-compose -f docker-compose.json up
Q10. Tell us how you have used Docker in your past position?
➢ Explain how you have used Docker to help rapid deployment. Explain how you have scripted Docker and used Docker with other tools like Puppet, Chef or Jenkins.
➢ If you have no past practical experience in Docker and have past experience with other tools in a similar space, be honest and explain the same. In this case, it makes sense if you can compare other tools to Docker in terms of functionality.
Q11. How to create Docker container?
I will suggest you to give a direct answer to this.
We can use Docker image to create Docker container by using the below command:
1
docker run -t -i command name
This command will create and start a container.
You should also add, If you want to check the list of all running container with the status on a host use the below command:
1
docker ps -a
Q12. How to stop and restart the Docker container?
In order to stop the Docker container you can use the below command:
1
docker stop container ID
Now to restart the Docker container you can use:
1
docker restart container ID
Q13 How far do Docker containers scale?
Large web deployments like Google and Twitter, and platform providers such as Heroku and dotCloud all run on container technology, at a scale of hundreds of thousands or even millions of containers running in parallel.
Q14. What platforms does Docker run on?
I will start this answer by saying Docker runs on only Linux and Cloud platforms and then I will mention the below vendors of Linux:
• Ubuntu 12.04, 13.04 et al
• Fedora 19/20+
• RHEL 6.5+
• CentOS 6+
• Gentoo
• ArchLinux
• openSUSE 12.3+
• CRUX 3.0+
Cloud:
• Amazon EC2
• Google Compute Engine
• Microsoft Azure
• Rackspace
Note that Docker does not run on Windows or Mac.
Q15. Do I lose my data when the Docker container exits?
You can answer this by saying, no I won’t lose my data when Docker container exits, any data that your application writes to disk gets preserved in its container until you explicitly delete the container. The file system for the container persists even after the container halts.
Q16. Mention some commonly used Docker command?
Below are some commonly used Docker commands:

Top 50 GIT interview questions

1) What is GIT?
GIT is a distributed version control system and source code management (SCM) system with an emphasis to handle small and large projects with speed and efficiency.
2) What is a repository in GIT?
A repository contains a directory named .git, where git keeps all of its metadata for the repository. The content of the .git directory are private to git.
3) What is the command you can use to write a commit message?
The command that is used to write a commit message is “git commit –a”. The –a on the command line instructs git to commit the new content of all tracked files that have been modified. You can use “git add<file>” before git commit –a if new files need to be committed for the first time.
4) What is the difference between GIT and SVN?
The difference between GIT and SVN is
a) Git is less preferred for handling extremely large files or frequently changing binary files while SVN can handle multiple projects stored in the same repository.
b) GIT does not support ‘commits’ across multiple branches or tags. Subversion allows the creation of folders at any location in the repository layout.
c) Gits are unchangeable, while Subversion allows committers to treat a tag as a branch and to create multiple revisions under a tag root.
5) What are the advantages of using GIT?
a) Data redundancy and replication
b) High availability
c) Only one.git directory per repository
d) Superior disk utilization and network performance
e) Collaboration friendly
f) Any sort of projects can use GIT
6) What language is used in GIT?
GIT is fast, and ‘C’ language makes this possible by reducing the overhead of runtimes associated with higher languages.
7) What is the function of ‘GIT PUSH’ in GIT?
‘GIT PUSH’ updates remote refs along with associated objects.
8) Why GIT better than Subversion?
GIT is an open source version control system; it will allow you to run ‘versions’ of a project, which show the changes that were made to the code overtime also it allows you keep the backtrack if necessary and undo those changes. Multiple developers can checkout, and upload changes and each change can then be attributed to a specific developer.
9) What is “Staging Area” or “Index” in GIT?
Before completing the commits, it can be formatted and reviewed in an intermediate area known as ‘Staging Area’ or ‘Index’.
10) What is GIT stash?
GIT stash takes the current state of the working directory and index and puts in on the stack for later and gives you back a clean working directory. So in case if you are in the middle of something and need to jump over to the other job, and at the same time you don’t want to lose your current edits then you can use GIT stash.
11) What is GIT stash drop?
When you are done with the stashed item or want to remove it from the list, run the git ‘stash drop’ command. It will remove the last added stash item by default, and it can also remove a specific item if you include as an argument.
12) How will you know in GIT if a branch has been already merged into master?
Git branch—merged lists the branches that have been merged into the current branch Git branch—-no merged lists the branches that have not been merged
13) What is the function of git clone?
The git clone command creates a copy of an existing Git repository. To get the copy of a central repository, ‘cloning’ is the most common way used by programmers.
14) What is the function of ‘git config’?
The ‘git config’ command is a convenient way to set configuration options for your Git installation. Behaviour of a repository, user info, preferences etc. can be defined through this command.
15) What does commit object contain?
a) A set of files, representing the state of a project at a given point of time
b) Reference to parent commit objects
c) An SHAI name, a 40 character string that uniquely identifies the commit object.
16) How can you create a repository in Git?
In Git, to create a repository, create a directory for the project if it does not exist, and then run command “git init”. By running this command .git directory will be created in the project directory, the directory does not need to be empty.
17) What is ‘head’ in git and how many heads can be created in a repository?
A ‘head’ is simply a reference to a commit object. In every repository, there is a default head referred as “Master”. A repository can contain any number of heads.
18) What is the purpose of branching in GIT?
The purpose of branching in GIT is that you can create your own branch and jump between those branches. It will allow you to go to your previous work keeping your recent work intact.
19) What is the common branching pattern in GIT?
The common way of creating branch in GIT is to maintain one as “Main“
branch and create another branch to implement new features. This pattern is particularly useful when there are multiple developers working on a single project.
20) How can you bring a new feature in the main branch?
To bring a new feature in the main branch, you can use a command “git merge” or “git pull command”.
21) What is a ‘conflict’ in git?
A ‘conflict’ arises when the commit that has to be merged has some change in one place, and the current commit also has a change at the same place. Git will not be able to predict which change should take precedence.
22) How can conflict in git resolved?
To resolve the conflict in git, edit the files to fix the conflicting changes and then add the resolved files by running “git add” after that to commit the repaired merge, run “git commit”. Git remembers that you are in the middle of a merger, so it sets the parents of the commit correctly.
23) To delete a branch what is the command that is used?
Once your development branch is merged into the main branch, you don’t need development branch. To delete a branch use, the command “git branch –d [head]”.
24) What is another option for merging in git?
“Rebasing” is an alternative to merging in git.
25) What is the syntax for “Rebasing” in Git?
The syntax used for rebase is “git rebase [new-commit] “
26) What is the difference between ‘git remote’ and ‘git clone’?
‘git remote add’ just creates an entry in your git config that specifies a name for a particular URL. While, ‘git clone’ creates a new git repository by copying and existing one located at the URI.
27) What is GIT version control?
With the help of GIT version control, you can track the history of a collection of files and includes the functionality to revert the collection of files to another version. Each version captures a snapshot of the file system at a certain point of time. A collection of files and their complete history are stored in a repository.
28) Mention some of the best graphical GIT client for LINUX?
Some of the best GIT client for LINUX is
a) Git Cola
b) Git-g
c) Smart git
d) Giggle
e) Git GUI
f) qGit
29) What is Subgit? Why to use Subgit?
‘Subgit’ is a tool for a smooth, stress-free SVN to Git migration. Subgit is a solution for a company - wide migration from SVN to Git that is:
a) It is much better than git-svn
b) No requirement to change the infrastructure that is already placed
c) Allows to use all git and all sub-version features
d) Provides genuine stress –free migration experience.
30) What is the function of ‘git diff ’ in git?
‘git diff ’ shows the changes between commits, commit and working tree etc.
31) What is ‘git status’ is used for?
As ‘Git Status’ shows you the difference between the working directory and the index, it is helpful in understanding a git more comprehensively.
32) What is the difference between the ‘git diff ’and ‘git status’?
‘git diff’ is similar to ‘git status’, but it shows the differences between various commits and also between the working directory and index.
33) What is the function of ‘git checkout’ in git?
A ‘git checkout’ command is used to update directories or specific files in your working tree with those from another branch without merging it in the whole branch.
34) What is the function of ‘git rm’?
To remove the file from the staging area and also off your disk ‘git rm’ is used.
35) What is the function of ‘git stash apply’?
When you want to continue working where you have left your work, ‘git stash apply’ command is used to bring back the saved changes onto the working directory.
36) What is the use of ‘git log’?
To find specific commits in your project history- by author, date, content or history ‘git log’ is used.
37) What is ‘git add’ is used for?
‘git add’ adds file changes in your existing directory to your index.
38) What is the function of ‘git reset’?
The function of ‘Git Reset’ is to reset your index as well as the working directory to the state of your last commit.
39) What is git Is-tree?
‘git Is-tree’ represents a tree object including the mode and the name of each item and the SHA-1 value of the blob or the tree.
40) How git instaweb is used?
‘Git Instaweb’ automatically directs a web browser and runs webserver with an interface into your local repository.
41) What does ‘hooks’ consist of in git?
This directory consists of Shell scripts which are activated after running the corresponding Git commands. For example, git will try to execute the post-commit script after you run a commit.
42) Explain what is commit message?
Commit message is a feature of git which appears when you commit a change. Git provides you a text editor where you can enter the modifications made in commits.
43) How can you fix a broken commit?
To fix any broken commit, you will use the command “git commit—amend”. By running this command, you can fix the broken commit message in the editor.
44) Why is it advisable to create an additional commit rather than amending an existing commit?
There are couple of reason
a) The amend operation will destroy the state that was previously saved in a commit. If it’s just the commit message being changed then that’s not an issue. But if the contents are being amended then chances of eliminating something important remains more.
b) Abusing “git commit- amend” can cause a small commit to grow and acquire unrelated changes.
45) What is ‘bare repository’ in GIT?
To co-ordinate with the distributed development and developers team, especially when you are working on a project from multiple computers ‘Bare Repository’ is used. A bare repository comprises of a version history of your code.
46) Name a few Git repository hosting services
Pikacode
Visual Studio Online GitHub GitEnterprise SourceForge.net

Top 10 Kubernetes interview questions

Q1. How is Kubernetes different from Docker Swarm?
Features Kubernetes Docker Swarm Installation & Cluster Config
Setup is very complicated, but once installed cluster is robust.
Installation is very simple, but the cluster is not robust. GUI
GUI is the Kubernetes Dashboard.
There is no GUI. Scalability
Highly scalable and scales fast.
Highly scalable and scales 5x faster than Kubernetes. Auto-scaling
Kubernetes can do auto-scaling.
Docker swarm cannot do auto-scaling. Load Balancing
Manual intervention needed for load balancing traffic between different containers and pods.
Docker swarm does auto load balancing
of traffic between containers in the cluster. Rolling Updates & Rollbacks
Can deploy rolling updates and does automatic rollbacks.
Can deploy rolling updates, but not automatic rollback. DATA Volumes
Can share storage volumes only with the other containers in the same pod.
Can share storage volumes with any other container. Logging & Monitoring
In-built tools for logging and monitoring.
3rd party tools like ELK stack should be used
for logging and monitoring.
Q2. What is Kubernetes?
Kubernetes is an open-source container management tool which holds the responsibilities of container deployment, scaling & descaling of containers & load balancing. Being the Google’s brainchild, it offers excellent community and works brilliantly with all the cloud providers. So, we can say that Kubernetes is not a containerization platform, but it is a multi-container management solution.
Q3. How is Kubernetes related to Docker?
It’s a known fact that Docker provides the lifecycle management of containers and a Docker image builds the runtime containers. But, since these individual containers have to communicate, Kubernetes is used. So, Docker builds the containers and these containers communicate with each other via Kubernetes. So, containers running on multiple hosts can be manually linked and orchestrated using Kubernetes.
Q4. What is the difference between deploying applications on hosts and containers?
➢ Refer to the above diagram. The left side architecture represents deploying applications on hosts. So, this kind of architecture will have an operating system and then the operating system will have a kernel which will have various libraries installed on the operating system needed for the application. So, in this kind of framework you can have n number of applications and all the applications will share the libraries present in that operating system whereas while deploying applications in containers the architecture is a little different.
➢ This kind of architecture will have a kernel and that is the only thing that’s going to be the only thing common between all the applications. So, if there’s a particular application which needs Java then that particular application we’ll get access to Java and if there’s another application which needs Python then only that particular application will have access to Python.
➢ The individual blocks that you can see on the right side of the diagram are basically containerized and these are isolated from other applications. So, the applications have the necessary libraries and binaries isolated from the rest of the system, and cannot be encroached by any other application.
Q5. What is Container Orchestration?
Consider a scenario where you have 5-6 microservices for an application. Now, these microservices are put in individual containers, but won’t be able to communicate without container orchestration. So, as orchestration means the amalgamation of all instruments playing together in harmony in music, similarly container orchestration means all the services in individual containers working together to fulfill the needs of a single server.
Q6. What is the need for Container Orchestration?
Consider you have 5-6 microservices for a single application performing various tasks, and all these microservices are put inside containers. Now, to make sure that these containers communicate with each other we need container orchestration.
As you can see in the above diagram, there were also many challenges that came into place without the use of container orchestration. So, to overcome these challenges the container orchestration came into place.
Q7. What are the features of Kubernetes?
The features of Kubernetes, are as follows:
Q8. How does Kubernetes simplify containerized Deployment?
As a typical application would have a cluster of containers running across multiple hosts, all these containers would need to talk to each other. So, to do this you need something big that would load balance, scale & monitor the containers. Since Kubernetes is cloud-agnostic and can run on any public/private providers it must be your choice simplify containerized deployment.
Q9. What do you know about clusters in Kubernetes?
The fundamental behind Kubernetes is that we can enforce the desired state management, by which I mean that we can feed the cluster services of a specific configuration, and it will be up to the cluster services to go out and run that configuration in the infrastructure.
So, as you can see in the above diagram, the deployment file will have all the configurations required to be fed into the cluster services. Now, the deployment file will be fed to the API and then it will be up to the cluster services to figure out how to schedule these pods in the environment and make sure that the right number of pods are running.
So, the API which sits in front of services, the worker nodes & the Kubelet process that the nodes run, all together make up the Kubernetes Cluster.
Q10. What is Google Container Engine?
Google Container Engine (GKE) is an open source management platform for Docker containers and the clusters. This Kubernetes based engine supports only those clusters which run within the Google’s public cloud services.
Q11. What is Heapster?
Heapster is a cluster-wide aggregator of data provided by Kubelet running on each node. This container management tool is supported natively on Kubernetes cluster and runs as a pod, just like any other pod in the cluster. So, it basically discovers all nodes in the cluster and queries usage information from the Kubernetes nodes in the cluster, via on-machine Kubernetes agent.
Q12. What is Minikube?
Minikube is a tool that makes it easy to run Kubernetes locally. This runs a single-node Kubernetes cluster inside a virtual machine.
Q13. What is Kubectl?
Kubectl is the platform using which you can pass commands to the cluster. So, it basically provides the CLI to run commands against the Kubernetes cluster with various ways to create and manage the Kubernetes component.
Q14. What is Kubelet?
This is an agent service which runs on each node and enables the slave to communicate with the master. So, Kubelet works on the description of containers provided to it in the PodSpec and makes sure that the containers described in the PodSpec are healthy and running.
Q15. What do you understand by a node in Kubernetes?
Q1. What are the different components of Kubernetes Architecture?
The Kubernetes Architecture has mainly 2 components – the master node and the worker node. As you can see in the below diagram, the master and the worker nodes have many inbuilt components within them. The master node has the kube-controller-manager, kube-apiserver, kube-scheduler, etcd. Whereas the worker node has kubelet and kube-proxy running on each node.
Q2. What do you understand by Kube-proxy?
Kube-proxy can run on each and every node and can do simple TCP/UDP packet forwarding across backend network service. So basically, it is a network proxy which reflects the services as configured in Kubernetes API on each node. So, the Docker-linkable compatible environment variables provide the cluster IPs and ports which are opened by proxy.
Q3. Can you brief on the working of the master node in Kubernetes?
Kubernetes master controls the nodes and inside the nodes the containers are present. Now, these individual containers are contained inside pods and inside each pod, you can have a various number of containers based upon the configuration and requirements. So, if the pods have to be deployed, then they can either be deployed using user interface or command line interface. Then, these pods are scheduled on the nodes and based on the resource requirements, the pods are allocated to these nodes. The kube-apiserver makes sure that there is communication established between the Kubernetes node and the master components.
Q4. What is the role of kube-apiserver and kube-scheduler?
The kube – apiserver follows the scale-out architecture and, is the front-end of the master node control panel. This exposes all the APIs of the Kubernetes Master node components and is responsible for establishing communication between Kubernetes Node and the Kubernetes master components.
The kube-scheduler is responsible for distribution and management of workload on the worker nodes. So, it selects the most suitable node to run the unscheduled pod based on resource requirement and keeps a track of resource utilization. It makes sure that the workload is not scheduled on nodes which are already full.
Q5. Can you brief about the Kubernetes controller manager?
Multiple controller processes run on the master node but are compiled together to run as a single process which is the Kubernetes Controller Manager. So, Controller Manager is a daemon that embeds controllers and does namespace creation and garbage collection. It owns the responsibility and communicates with the API server to manage the end-points.
So, the different types of controller manager running on the master node are :
Q6. What is ETCD?
Etcd is written in Go programming language and is a distributed key-value store used for coordinating between distributed work. So, Etcd stores the configuration data of the Kubernetes cluster, representing the state of the cluster at any given point in time.
Q7. What are the different types of services in Kubernetes?
The following are the different types of services used:
Q8. What do you understand by load balancer in Kubernetes?
A load balancer is one of the most common and standard ways of exposing service. There are two types of load balancer used based on the working environment i.e. either the Internal Load Balancer or the External Load Balancer. The Internal Load Balancer automatically balances load and allocates the pods with the required configuration whereas the External Load Balancer directs the traffic from the external load to the backend pods.
Q9. What is Ingress network, and how does it work?
Ingress network is a collection of rules that acts as an entry point to the Kubernetes cluster. This allows inbound connections, which can be configured to give services externally through reachable URLs, load balance traffic, or by offering name-based virtual hosting. So, Ingress is an
API object that manages external access to the services in a cluster, usually by HTTP and is the most powerful way of exposing service.
Now, let me explain to you the working of Ingress network with an example.
There are 2 nodes having the pod and root network namespaces with a Linux bridge. In addition to this, there is also a new virtual ethernet device called flannel0(network plugin) added to the root network.
Now, suppose we want the packet to flow from pod1 to pod 4. Refer to the below diagram.
• So, the packet leaves pod1’s network at eth0 and enters the root network at veth0.
• Then it is passed on to cbr0, which makes the ARP request to find the destination and it is found out that nobody on this node has the destination IP address.
• So, the bridge sends the packet to flannel0 as the node’s route table is configured with flannel0.
• Now, the flannel daemon talks to the API server of Kubernetes to know all the pod IPs and their respective nodes to create mappings for pods IPs to node IPs.
• The network plugin wraps this packet in a UDP packet with extra headers changing the source and destination IP’s to their respective nodes and sends this packet out via eth0.
• Now, since the route table already knows how to route traffic between nodes, it sends the packet to the destination node2.
• The packet arrives at eth0 of node2 and goes back to flannel0 to de-capsulate and emits it back in the root network namespace.
• Again, the packet is forwarded to the Linux bridge to make an ARP request to find out the IP that belongs to veth1.
• The packet finally crosses the root network and reaches the destination Pod4.
Q10. What do you understand by Cloud controller manager?
The Cloud Controller Manager is responsible for persistent storage, network routing, abstracting the cloud-specific code from the core Kubernetes specific code, and managing the communication with the underlying cloud services. It might be split out into several different containers depending on which cloud platform you are running on and then it enables the cloud vendors and Kubernetes code to be developed without any inter-dependency. So, the cloud vendor develops their code and connects with the Kubernetes cloud-controller-manager while running the Kubernetes.
The various types of cloud controller manager are as follows:
Q11. What is Container resource monitoring?
As for users, it is really important to understand the performance of the application and resource utilization at all the different abstraction layer, Kubernetes factored the management of the cluster by creating abstraction at different levels like container, pods, services and whole cluster. Now, each level can be monitored and this is nothing but Container resource monitoring.
The various container resource monitoring tools are as follows:
Q12. What is the difference between a replica set and replication controller?
Replica Set and Replication Controller do almost the same thing. Both of them ensure that a specified number of pod replicas are running at any given time. The difference comes with the usage of selectors to replicate pods. Replica Set use Set-Based selectors while replication controllers use Equity-Based selectors.
• Equity-Based Selectors: This type of selector allows filtering by label key and values. So, in layman terms, the equity-based selector will only look for the pods which will have the exact same phrase as that of the label. Example: Suppose your label key says app=nginx, then, with this selector, you can only look for those pods with label app equal to nginx.
• Selector-Based Selectors: This type of selector allows filtering keys according to a set of values. So, in other words, the selector based selector will look for pods whose label has been mentioned in the set. Example: Say your label key says app in (nginx, NPS, Apache). Then, with this selector, if your app is equal to any of nginx, NPS, or Apache, then the selector will take it as a true result.
Q13. What is a Headless Service?
Headless Service is similar to that of a ‘Normal’ services but does not have a Cluster IP. This service enables you to directly reach the pods without the need of accessing it through a proxy.
Q14. What are the best security measures that you can take while using Kubernetes?
The following are the best security measures that you can follow while using Kubernetes:
Q15. What are federated clusters?
Multiple Kubernetes clusters can be managed as a single cluster with the help of federated clusters. So, you can create multiple Kubernetes clusters within a data center/cloud and use federation to control/manage them all at one place.
The federated clusters can achieve this by doing the following two things. Refer to the below diagram.
cenario 1: Suppose a company built on monolithic architecture handles numerous products. Now, as the company expands in today’s scaling industry, their monolithic architecture started causing problems.
How do you think the company shifted from monolithic to microservices and deploy their services containers?
Solution:
As the company’s goal is to shift from their monolithic application to microservices, they can end up building piece by piece, in parallel and just switch configurations in the background. Then they can put each of these built-in microservices on the Kubernetes platform. So, they can start by migrating their services once or twice and monitor them to make sure everything is running stable. Once they feel everything is going good, then they can migrate the rest of the application into their Kubernetes cluster.
Scenario 2: Consider a multinational company with a very much distributed system, with a large number of data centers, virtual machines, and many employees working on various tasks.
How do you think can such a company manage all the tasks in a consistent way with Kubernetes?
Solution:
As all of us know that I.T. departments launch thousands of containers, with tasks running across a numerous number of nodes across the world in a distributed system.
In such a situation the company can use something that offers them agility, scale-out capability, and DevOps practice to the cloud-based applications.
So, the company can, therefore, use Kubernetes to customize their scheduling architecture and support multiple container formats. This makes it possible for the affinity between container tasks that gives greater efficiency with an extensive support for various container networking solutions and container storage.
Scenario 3: Consider a situation, where a company wants to increase its efficiency and the speed of its technical operations by maintaining minimal costs.
How do you think the company will try to achieve this?
Solution:
The company can implement the DevOps methodology, by building a CI/CD pipeline, but one problem that may occur here is the configurations may take time to go up and running. So, after implementing the CI/CD pipeline the company’s next step should be to work in the cloud environment. Once they start working on the cloud environment, they can schedule containers on a cluster and can orchestrate with the help of Kubernetes. This kind of approach will help the company reduce their deployment time, and also get faster across various environments.
Scenario 4: Suppose a company wants to revise it’s deployment methods and wants to build a platform which is much more scalable and responsive.
How do you think this company can achieve this to satisfy their customers?
Solution:
In order to give millions of clients the digital experience they would expect, the company needs a platform that is scalable, and responsive, so that they could quickly get data to the client website. Now, to do this the company should move from their private data centers (if they are using any) to any cloud environment such as AWS. Not only this, but they should also implement the microservice architecture so that they can start using Docker containers. Once they have the base framework ready, then they can start using the best orchestration platform
available i.e. Kubernetes. This would enable the teams to be autonomous in building applications and delivering them very quickly.
Scenario 5: Consider a multinational company with a very much distributed system, looking forward to solving the monolithic code base problem.
How do you think the company can solve their problem?
Solution
Well, to solve the problem, they can shift their monolithic code base to a microservice design and then each and every microservices can be considered as a container. So, all these containers can be deployed and orchestrated with the help of Kubernetes.
Scenario 6: All of us know that the shift from monolithic to microservices solves the problem from the development side, but increases the problem at the deployment side.
How can the company solve the problem on the deployment side?
Solution
The team can experiment with container orchestration platforms, such as Kubernetes and run it in data centers. So, with this, the company can generate a templated application, deploy it within five minutes, and have actual instances containerized in the staging environment at that point. This kind of Kubernetes project will have dozens of microservices running in parallel to improve the production rate as even if a node goes down, then it can be rescheduled immediately without performance impact.
Scenario 7: Suppose a company wants to optimize the distribution of its workloads, by adopting new technologies.
How can the company achieve this distribution of resources efficiently?
Solution
The solution to this problem is none other than Kubernetes. Kubernetes makes sure that the resources are optimized efficiently, and only those resources are used which are needed by that particular application. So, with the usage of the best container orchestration tool, the company can achieve the distribution of resources efficiently.
Scenario 8: Consider a carpooling company wants to increase their number of servers by simultaneously scaling their platform.
How do you think will the company deal with the servers and their installation?
Solution
The company can adopt the concept of containerization. Once they deploy all their application into containers, they can use Kubernetes for orchestration and use container monitoring tools like Prometheus to monitor the actions in containers. So, with such usage of containers, giving them better capacity planning in the data center because they will now have fewer constraints due to this abstraction between the services and the hardware they run on.
Scenario 9: Consider a scenario where a company wants to provide all the required hand-outs to its customers having various environments.
How do you think they can achieve this critical target in a dynamic manner?
Solution
The company can use Docker environments, to put together a cross-sectional team to build a web application using Kubernetes. This kind of framework will help the company achieve the goal of getting the required things into production within the shortest time frame. So, with such a machine running, the company can give the hands-outs to all the customers having various environments.
Scenario 10: Suppose a company wants to run various workloads on different cloud infrastructure from bare metal to a public cloud.
How will the company achieve this in the presence of different interfaces?
Solution
The company can decompose its infrastructure into microservices and then adopt Kubernetes. This will let the company run various workloads on different cloud infrastructures.
Q1. What are minions in Kubernetes cluster?
a. They are components of the master node.
b. They are the work-horse / worker node of the cluster.[Ans]
c. They are monitoring engine used widely in kubernetes.
d. They are docker container service.
Q2. Kubernetes cluster data is stored in which of the following?
a. Kube-apiserver
b. Kubelet
c. Etcd[Ans]
d. None of the above
Q3. Which of them is a Kubernetes Controller?
a. ReplicaSet
b. Deployment
c. Rolling Updates
d. Both ReplicaSet and Deployment[Ans]
Q4. Which of the following are core Kubernetes objects?
a. Pods
b. Services
c. Volumes
d. All of the above[Ans]
Q5. The Kubernetes Network proxy runs on which node?
a. Master Node
b. Worker Node
c. All the nodes[Ans]
d. None of the above
Q6. What are the responsibilities of a node controller?
a. To assign a CIDR block to the nodes
b. To maintain the list of nodes
c. To monitor the health of the nodes
d. All of the above[Ans]
Q7. What are the responsibilities of Replication Controller?
a. Update or delete multiple pods with a single command
b. Helps to achieve the desired state
c. Creates a new pod, if the existing pod crashes
d. All of the above[Ans]
Q8. How to define a service without a selector?
a. Specify the external name[Ans]
b. Specify an endpoint with IP Address and port
c. Just by specifying the IP address
d. Specifying the label and api-version
Q9. What did the 1.8 version of Kubernetes introduce?
a. Taints and Tolerations[Ans]
b. Cluster level Logging
c. Secrets
d. Federated Clusters
Q10. The handler invoked by Kubelet to check if a container’s IP address is open or not is?
a. HTTPGetAction
b. ExecAction
c. TCPSocketAction[Ans]
d. None of the above