## DevOps : The next big game changer

If you’re a hard core techie, and stay updated with current trends in the IT world, chances are that you’ve already heard of the term DevOps. But just what is it all about, anyway, and why is it touted to be the next big game changer? DevOps is a movement that has been brought about in the software industry by people who think it’s high time there is a change. For too many years now, it has been tacitly understood that if you are working on a software project, it is bound to run late, exceed the budget, and underperform. A sorry state of affairs indeed, but yes, this is the way things have been! So we have had these all-too familiar situations outlined below: No one is confident whether the software will actually work when deployed Problems manifest the moment the site goes live It is very hard or impossible to change an application, once delivered Teams tend to ‘pass the buck’- developers blame testers, who blame release managers. And so on, and so forth. We’ve all been there, and done that. But there are some folks who actually decided to do something about this situation. And that’s how the concept of DevOps was born. The DevOps movement was started by some people who believed that by combining technology and changing the attitude of teams, software development and delivery can be revolutionized. “DevOps” is a portmanteau of ‘development’ and ‘operations’, with the buzzwords being communication, collaboration, integration, automation and cooperation. The DevOps approach clearly is a win-win situation, and is an understanding of how collaboration between developers and operations staff can create value at all stages of the product lifecycle. DevOps leans toward extending basic Agile and Lean principles, in a manner that includes the overall services, including systems and operations. In the DevOps world of the future, the paradigm has shifted and boundaries have blurred. Will this movement catch on? Let’s wait and watch.
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# DevOps : The next big game changer

547

If you’re a hard core techie, and stay updated with current trends in the IT world, chances are that you’ve already heard of the term DevOps. But just what is it all about, anyway, and why is it touted to be the next big game changer?

DevOps is a movement that has been brought about in the software industry by people who think it’s high time there is a change. For too many years now, it has been tacitly understood that if you are working on a software project, it is bound to run late, exceed the budget, and underperform. A sorry state of affairs indeed, but yes, this is the way things have been!

So we have had these all-too familiar situations outlined below:

• No one is confident whether the software will actually work when deployed
• Problems manifest the moment the site goes live
• It is very hard or impossible to change an application, once delivered
• Teams tend to ‘pass the buck’- developers blame testers, who blame release managers. And so on, and so forth.

We’ve all been there, and done that. But there are some folks who actually decided to do something about this situation. And that’s how the concept of DevOps was born.

The DevOps movement was started by some people who believed that by combining technology and changing the attitude of teams, software development and delivery can be revolutionized. “DevOps” is a portmanteau of ‘development’ and ‘operations’, with the buzzwords being communication, collaboration, integration, automation and cooperation.

The DevOps approach clearly is a win-win situation, and is an understanding of how collaboration between developers and operations staff can create value at all stages of the product lifecycle. DevOps leans toward extending basic Agile and Lean principles, in a manner that includes the overall services, including systems and operations.

In the DevOps world of the future, the paradigm has shifted and boundaries have blurred. Will this movement catch on? Let’s wait and watch.

### Usha Sunil

Blog Author

Writing is Usha's hobby and passion. She has written widely on topics as diverse as training, finance, HR and marketing, and is now into technical writing and education. She keeps an interested eye on new trends in technology, and is currently on a mission to find out what makes the world go around.

Great article!

Before we start discussing the salary of DevOps Engineer, let’s understand what DevOps is? DevOps is a software development strategy which bridges the gap between the developers and the IT staff. It enables organizations to release small features very quickly and incorporate the feedback which they receive very quickly. Its benefits are less software failure and shortened the lead time between fixes.As a DevOps Engineer, you get a clear understanding of the Software Development Lifecycle along with various automation tools for developing digital pipelines (CI/CD pipelines). Glassdoor ranks DevOps at second among the 50 Best Jobs in America. But who can become a DevOps Engineer? The journey of becoming a DevOps Engineer is pretty long. However, you can become a DevOps Engineer even as a fresher. Further, working as a Developer, Ops person, Quality Assurance also prepares you to work in this role. The 2019 Tech Salary Report released by Dice shows that the salary of DevOps Engineer ranks in the Top 5 salaries with an average of $111,683.According to Experts, the popularity of DevOps is going to reach its peak in 2019. The above chart shows the Google trend for the term DevOps in the year 2019 projecting a hypothesis of its growth.Salary of DevOps EngineerWith all the skills and expertise as a DevOps Engineer, it is important for you to know where you stand in terms of salary. The salary you can earn as a DevOps Engineer in the major countries are as follows:CountriesCurrenciesSalary of DevOps Engineer (per annum)IndiaINR6,42,692UKPound Sterling40,883USAUSD92,054CanadaCAD76,357Experience also plays a pivotal role while determining your salary. Now let’s take a look at the experience-wise salary of DevOps Engineer across the globe:CountriesCurrenciesSalary of DevOps Engineer (per annum)Entry-levelMid-CareerExperiencedIndiaINR3,52,23310,47,56716,12,255UKPound Sterling29,59848,56160,629USAUSD72,966100,576117,161CanadaCAD61,19182,27789,198Further, the maximum and minimum salaries that DevOps Engineers earn in the above-mentioned countries can be seen in the following chart:CountriesCurrenciesMinimum Salary (per annum)Maximum Salary (per annum)IndiaINR3,07,00020,00,000UKPound Sterling26,00067,000USAUSD63,000134,000CanadaCAD55,00099,000Company-wise salary in various countriesAs we have seen the average as well as the minimum and maximum salary in the major countries, now let’s take a look at a company-wise salary in those countries. First, let’s take a look at the top companies hiring DevOps Engineers in India and the salary paid by them:Company NameAverage Salary (per annum in INR)Tata Consultancy Services4,92,545Accenture6,40,043IBM4,35,534Cognizant Technology Solutions4,43,759Amazon11,15,053Now, let’s take a look at the average salary paid by the top companies to DevOps Engineer in the United Kingdom:Company NameAverage Salary (per annum in £)Cloudreach35,222Accenture33,198KPMG58,575ClearScore55,827Sky44,642The top companies hiring DevOps Engineer in the United States and the salaries offered to them are as follows:Company NameAverage Salary (per annum in$)IBM112,432Cognizant Technology Solutions96,381Accenture107,086Amazon110,779Capital One100,344The following are the top companies hiring DevOps Engineer in Canada and the salaries offered to them are as follows:Company NameAverage Salary (per annum in CA$)IBM104,170Cloudreach74,068SAP105,500Blackberry89,500Global Relay83,544Why DevOps Engineers are paid highly?DevOps is one of the most spoken and popular terms in IT. As you can see in the above charts that apart from being in demand, DevOps can set you on a promising journey in terms of your career prospects. Now let’s take a look at a few reasons which make DevOps Engineer the most demanded job:1. High ROIDid you ever imagine why companies are ready to invest in paying high salaries to DevOps Engineers? The reason for the demand is high ROI. Implementation of DevOps helps an organisation to increase its annual profit, resulting in companies searching for such engineers.2. DevOps lead the futureReports tell that DevOps is going to remain an essential part of IT projects. This is another reason that leads to high demand in job. This increase in demand for hiring DevOps engineers as the experts believe that it’s going to be more vital for businesses in the future.3. It’s cloud-basedIn this era, when most of the applications are changing to cloud-based platforms, you might be glad to know that it’s important for you to have some DevOps experts by your side. The clouds and infrastructural processes applied through DevOps are complementary. Organisations need to deploy proper processes to successfully change the applications in the main platform. This is the core reason behind IT projects and businesses looking to hire DevOps Engineers.4. Triggers sufficiencyDevOps focuses on increasing the sufficiency. You are able to interact with the applications easily as well as all the changes are confirmed a fast as possible once you apply the practices and updates more frequently. This reduced reputation-threatening errors.5. CompetitiveAnother reason for DevOps’ demand is that it is capable of pushing you up the list. From IT-based company to business application company, DevOps can keep it going without fail.On a concluding noteTo conclude, a DevOps Engineer is equipped with the skills of testing, building, integrating, coding, and deployment along with problem-solving skills. Also, as a DevOps Engineer, you need to multitask and handle challenges that arise from multiple roles in order to justify your designation. It is suggestible to opt for a DevOps training with a reputed training provider and get DevOps certified to explore its benefits.The skills and expertise that you possess as a DevOps Engineer also makes you eligible to move towards a promising career with a good salary. This blog will give you a clear idea about the earning prospect around the globe as well as the top companies hiring DevOps Engineers across the globe. All the best for your DevOps career! Rated 4.5/5 based on 5 customer reviews 9786 DevOps Engineer Salary Before we start discussing the salary of DevOps En... Read More ## Making DevOps Applicable For You In summary, DevOps is a philosophy of software development that focuses on meeting business requirements quickly and efficiently. It helps shorten time to value and in so doing helps create a more responsive organization. It multiplies the value from investments in cloud and encourages automation of key processes for better outcomes. All of which makes it highly suitable to cost constrained organizations that must deliver improvements to their current services and products while taking advantage of the opportunities presented by new digital and data-driven technologies. However, the advantages of the DevOps helping for organizations in large scale. The long-term cost reductions are substantial, but the initial investment can be high. Although automation delivers a strong return on initial investment of time and resources, it does take longer to complete this initial automation of a task that it does to perform the same task manually. Maintaining the DevOps approach will also require specific technical skills to be build up, managed and retained by the implementation organization as well as the client organization. So, how do you make sure that the adoption of the DevOps approach works for your organization? The following can be those critical factors. Senior management buy-in As with all change projects, success is in part dependent on having committed leaders at senior leadership levels; in this case the CIO, CTO or the chief architect (and even the enterprise architect of the client organization) who can deliver technical and cultural changes. They are responsible for making sure the focus remains on breaking down the barriers between development and operations and ensuring the approach is designed around this core principle. They need to make sure that close collaboration between developers, system operators and testers is maintained and that open lines of communication with business users and service commissioners remain intact. Understand the demands of digital transformation It is important to understand the demands of digital transformation and balance it with the rigour of ITIL. At present, only about 5% of services of organizations are driven by technologies that are digital by design. Applying DevOps to these technologies is relatively straightforward. But mission-critical platforms on physical or virtual servers are a different question altogether. An iterative approach to migrating these applications to the cloud, taking small steps to transformation and applying DevOps one step at a time requires not just digital skills but the depth of understanding residing in experienced IT managers. Need for security, compliance and governance It is important to ensure that testing and security are built into the automated processes of the implementing organization. Those processes must stay true to ITIL standards for security testing and compliance checking. Even at this pace software can only be put into production when it has no vulnerabilities that can corrupt sensitive information. DevOps does not replace the need for quality assurance, software testing or data validation before and after a software release. Hence it is important to get the QA practices with regards to automated testing for security, performance and code check-ins and check-outs in top shape. Work with the right people Some IT services service providers are great at automation or at building digital services. Bringing them together is the key. This means that IT practitioners who already have wide experience of delivering systems under the DevOps umbrella and are prepared to share best practice and ensure effective knowledge transfer are a key part of the team. So are leaders with expertise in automating business and management processes and have a well defined and tested set of tools to support their work. It is important for client organizations to look for service providers with real, in-depth experience of open technologies, domain expertise and cloud-based solutions and with the necessary hands-on experience in designing, building, migrating, supporting and operating scalable and robust systems for their customers. Rated 4.0/5 based on 20 customer reviews 342 Making DevOps Applicable For You In summary, DevOps is a philosophy of software dev... Read More ## Docker Vs Virtual Machines(VMs) Let’s have a quick warm up on the resource management before we dive into the discussion on virtualization and dockers.In today’s multi-technology environments, it becomes inevitable to work on different software and hardware platforms simultaneously.The need to run multiple different machines (Desktops, Laptops, handhelds, and Servers) platforms with customized hardware and software requirements has given the rise to a new world of virtualization in IT industry.What a machine need?Each computing environment(machine) needs its own component of hardware resources and software resources.As more and more machines are needed, building up and administering many such stand-alone machines is not only cumbersome, time consuming but also adds up to the cost and energy.Apparently; to run a customized High-power Scalable Server is a better idea to consolidate all the hardware and software requirements into one place and have a single server run and distribute the resources to many machines over a network.That saves us time, resources, energy and revenue.These gigantic servers are stored in a data warehouse called a Datacenter.Below Diagram (2) indicates a single server serving and sharing resources and data among multiple client machinesDoes this look simplified enough? Yes of course!So, this setup looks feasible we have a high-power, high-storage Server that gives resources to many smaller(resources) machines over a network.How to manage huge data - ServersWith Internet Of Things in boom, Information is overflowing with a huge amount of data; handling tremendous data needs more system resources which means more Dedicated servers are needed.Many Servers approach challenge:Running several Dedicated servers for specific services such as Web service, application or database service as indicated in Diagram (3) is difficult to administer and consumes more energy, resources, manpower and is highly expensive.In addition; resource utilization of servers is very poor resulting in resource wastage.This is where simulating different environments and running them all on a single server is a smart choice; rather than having to run multiple physically distinct servers.This is how Diagram (3) would change after consolidating different servers into one as shown in Diagram (4).Sheet 2VirtualizationWhat is VirtualizationThe above single server implementation can be defined as the following term.Virtualization is a technique used to simulate and pretend a single infrastructure resource (hardware resources and software resources) to be acting as many providing multiple functionalities or services without the need to physically build, install and configure.In other words;Running multiple simulated environments in a single machine without installing and configuring them is called Virtualization.Technically speaking;Virtualization is an abstract layer that shares the infrastructure resources among various simulated virtual machines without the need to physically set up these environments.Diagram (5) displays different virtual Operating systems are running on the same machine and using the same hardware architecture of the underlying machine.What is a Virtual machineThe simulated virtualized environments are called virtual machines or VM.Virtual machine is a replication/simulation of an actual physical machine.A VM acts like a real physical machine and uses the physical resources of the underlying host OS.A VM is a running instance of a real physical machine.Need for virtualizationSo; we have an overview of virtualization, let us examine when should we virtualize and what are the benefits of virtualization?Better resource management and cost-effective: as indicated in Diagram (6) and Diagram (7); hardware resources are distributed wisely on need basis to different environments; all the virtual machines share the same resources and reduce resource wastage.Ease of quick administration and maintenance: It is easier to build, install, configure one server rather than multiple servers. Updating a patch on various machines from a single virtualized server is much more feasible.Disaster recovery: Since all the virtualized machines reside on the same server and are treated as mounted volumes of data files, it is easier to back up these machines. In case of a disaster failure (power failure, network down, cyber-attacks, failed test code, etc) VM screenshots are used to recover the running state of the machine and the whole setup can be built up within minutes.Isolated and independent secure test environment: virtualization provide an isolated independent virtual test environment to test the legacy code or a vendor-specific product or even a beta release or say a corrupt code without affecting the main hardware and software platform. (This is a contradictory statement though; will discuss more under types of virtualization)These test environments like dev, uat, preprod, prod etc..can be easily tested and discarded.Easily scalable and upgradable: Building up more simulated environments means spinning up more virtual machines. Also upgrading VMs is as good as to run a patch in all VMs.Portable: Virtual machines are lightweight compared to the actual running physical machines; in addition, a VM that includes its own OS, drivers, and other installation files is portable on any machine. One can access the data virtually from any location.The screenshot of activity monitor below compares the CPU load:Implementation a) What is hypervisor and its types?As discussed in the previous section; virtualization is achieved by means of a virtualized layer on top of hardware or a software resource.This abstract layer is called a hypervisor.A hypervisor is a virtual machine monitor (VMM)There are 2 types of hypervisors: Diagram (8)Type-1 or bare-metal hypervisorType-2 or hosted hypervisorType-1 or bare-metal hypervisor is installed directly on the system hardware, thus abstracting and sharing the hardware components with the VMs.Type-2 or hosted hypervisor is installed on top of the system bootable OS called host OS; this hypervisor abstracts the system resources visible to the host OS and distributes it among the VMs.Both have their own role to play in virtualization.b) Comparing hypervisor typesType-1 or bare-metal hypervisorType-2 or hosted hypervisorInstalled directly on the infrastructure-OS independent and more secure against software issues.Installed on top of the host OS-more prone to software failures.Better resource flexibility: Have direct access to the hardware infrastructure (Hard-drive partition, RAM, embedded cards such as NIC). Provide more flexibility and scalability to the VMs and assign resources on a need basis.Limited resource allocation: Have access to just the resources exposed by the host OS.VMs installed will have limited access to hardware resources allocated and exposed by the host OS.Single point of failure: A compromised VM may affect the kernel. Extra security layers needed.A compromised VM may affect only the host OS, kernel still remains unreachable.Low latency due to direct link to the infrastructure.High latency as all the VMs have to pass through the OS layer to access the system resources.Generally used in ServersGenerally used on small client machinesExpensiveLess expensiveType-1 Hypervisors in market:VMWare ESX/ESXiHyperkit (OSX)Microsoft Hyper-V (Windows)KVM(Linux)Oracle VM ServerType-2 Hypervisors in market:Oracle VM VirtualBoxVMWare WorkstationParallels desktop for MACTypes of virtualizationBased on what resource is virtualized, there are different classifications of virtualization.Server, Storage device, operating system, networkDesktop virtualization: Entire desktop environment is simulated and distributed to run on a single server all at once. A desktop virtualization allows administrators to manage, install, configure similar setups on many machines. Upgrading all the machines with a single patch update or security checks becomes easier and faster.Server virtualization: Many dedicated servers can be virtualized into a single server that provides multi-server functionality.Example:Many virtual machines can be built up sharing the same underlying system resources.Storage, RAM, disks, CPUOperating system virtualization: This happens at the kernel level Hypervisor on hardware type 2 bare-metal One machine: Can boot up as multiple OS like Windows or Linux side-by-sideApplication virtualization: Apps are packaged and stored in a virtual environment and are distributed across different VMs. Example Microsoft applications like excel, MS word, Powerpoint etc, Citrix applications.Network functions virtualization: Physical network components such as NIC cards, switches, routers, servers, hubs, and cables are all assembled in a single server and used virtually by multiple machines without having the load of installing them on every machine.Virtualization is one of the building blocks and driving force behind cloud computing.Cloud computing provide virtualized need-based services. This has given an uplift to the concept of virtualization.A quick mention of various cloud computing models/services are listed below:SaaS – Software as a Service– end-user applications are maintained and run by service providers and easily distributed and used by the end users without having to install them.Top SaaS providers: Microsoft (Office suite, CRM, SQL server databases), AWS, Adobe, Oracle (ERP, CRM, SCM), Cisco’s Webex, GitHub ( git hosting web service)PaaS – Platform as a Service – computing infrastructure(hardware/software) is maintained and updated by the service provider and the user just have to run the product over this platform.Top Paas providers: AWS beanstalk, Oracle Cloud Platform (OCP), Google App EngineIaaS – Infrastructure as a Service – Provide infrastructure such as servers, physical storage, networking, memory devices etc. Users can build their own platform with customized operating system and applications.Key IaaS providers: Amazon Web Services, Microsoft Azure, Google compute engine, CitrixConclusion:We now have a fair understanding of types of virtualization and how they are implemented.ContainerizationThough virtualization has its pros; there are certain downsides of virtualization such as:Not all systems can be virtualized always.A corrupt VM is sometimes contagious and may affect other VMs or the kernel in-case of a Type-1 or bare-metal hypervisor.Latency of virtual disks due to increased payload on the CPU resources with a higher number of VMsUnstable performanceAn alternative approach to overcome the above flaws of virtualization is to Containerize the applications and the run-time environment together.What is containerization Containerization is an OS-level virtualization; wherein the entire build of an application along with run-time environment is encapsulated or bundled up in a package.These packages are called containers.Containers are lightweight virtualized environments. These are independent of the infrastructure both hardware and software.The run-time environment includes the operating system, binaries, libraries, configuration files and other applications as shown in Diagram (9).What is DockersDockers provide an excellent framework for containerization and allow to build, ship, and run distributed applications over multiple platforms.Docker framework is setup as a docker engine installed on host OS and a docker daemon (background process) process is started that manage the virtual containers.Refer Diagram (10) that shows a Docker engine with 3 containers residing on host OS (MAC OS).An instruction file called dockerfile is written with a set of system commands that change the filesystem such as add, copy or delete commands, run commands, install utilities, system calls etc…This dockerfile is built and packaged along with its run-time environment as an executable file called a docker image.Docker daemon services run these images to create docker containers.Docker container is a run-time instance of an imageIt is wise to say that many images (or layers of instruction files) make up a container.Docker containers have a compact packaging and each container is well isolated.We can run, start, stop, attach, move or delete containers as these runs as services on the host OS.Each image is made up of different layers; each image based on top of the other with the customized command changes that we make.Every time we make a change in the filesystem, each change related to the image is encapsulated in a new layer of filesystem and stacked up above the parent image.Only the changed layers are rebuilt, rest of the unchanged image layers are reused.Certain docker commands ADD, RUN and COPY create a new layer with increased byte size; rest of the commands simply adds up a new layer with zero-byte size.These layers are re-used to build a new image, hence faster and lightweight.Docker images are alsoThe layer approach of an image every time there is a change in the image makes it possible to Version control the docker images.Here is a terminal recording that shows docker engine process and how images and containers are created.Docker documentation - to create containers.Ppt diagram:Code -> package -> build images -> registry hub -> download/pull image -> run containerAnimation: sheet4Let’s consider the docker container: divyabhushan/learn_docker hosted on docker hub.Latest tagged image: centOS_release1.2What is the container environment?Base OS: Centos:7Utilities: vim, yum, gitApps/files: Dockerfile, myApp.sh, runtests.sh, data and other supporting files.Git source code: dockerImagesDownload as: git clone https://github.com/divyabhushan/DockerImages_Ubuntu.gitWhat does the container do?Container launches “myApp.sh” in Ubuntu:14.04 environment and run some scripts along with a set of post test_suites in the container (Ubuntu:14.04) and saves the output log file.How to modify and build your own appStep 1: pull 1.1: Pull the docker image1.2: Run image to create a container and exitStep 2: modify2.1: Start the container2.2: Attach to the container and make some changesStep 3: commit3.1: Examine the history logs and changes in the container3.2: Commit the changes in containerStep 4: push4.1: Push new image to docker hubLet us see the steps in action:Step 1: pull docker image on your machine1.1: Pull the docker imageCommand:docker pull divyabhushan/learn_docker:myApp_ubuntu_14.04View the image on systemdocker imagesscreenshotCommand:docker run -it --name ubuntu14.04 0a6f949131a6Run command in ubuntu container and exit, the container is stopped on exiting out.View the stopped container with the ‘ps -a’ command.Step 2: modifyStart the containerCommand:docker start Now the container is listed as a running process Attach to the container and make some changesCommand:docker attach 7d0d0225778cedit the ‘git configuration’ file and ‘myApp.sh’ scriptContainer is modified and stoppedStep 3: commitExamine the history logs and changes in the containerThe changes done inside the container filesystem can be viewed using the ‘docker diff’ command as:Command: docker diff 7d0d0225778cCommit the changes in containerDocker commit:Usage: docker commit [OPTIONS] CONTAINER [REPOSITORY[:TAG]]docker commit -m 'new Ubuntu image' 7d0d0225778c divyabhushan/learn_docker:ubuntu14.04_v2New image is created and listedStep 4: pushPush new image to docker hubCommand:docker push divyabhushan/learn_docker:ubuntu14.04_v2Point to note: just the latest commit change layer ‘50a5ce553bba’ has been pushed, while the other layers were re-used.Image available on docker hub:The latest tagged image can now be pulled from other machines; and run to create the same container environment.Conclusion: An image was pulled and run to create a container to replicate the environment. Container was modified, new changes were committed to form a new image. New Image pushed back on the docker hub and now available as a new tag ready to be pulled by other machines.Difference between Dockers and Virtual machinesTabular differences on various parametersParametersVMsDockersarchitectureHardware level virtualization. Each VM has its own copy of OS.Software level virtualization. Dockers have no own OS, run on host OSIsolationFully isolatedProcess or application-level isolation. InstallationHypervisor can run directly on the hardware resources or on the host OS.Docker engine is installed on top of the host OS. A docker daemon process is initiated on the host OS. There is no separate OS for every container.CPU processing + performanceSlower: A VM contains the entire run-time environment that has to be loaded every time. Uses more CPU cycles; gives unstable performance.Faster: Docker images are pre-built and share host resources as a result running an image as a container is lightweight and consumes less CPU cycle; gives a stable performanceHardware storageMore storage space as each VM is an independent machine (OS). Example: 3 VMs of 800MB each will take 2.4 GB of space.Docker containers are lightweight since do not require to load OS+drivers, run on host OS as processes.PortableDependency on host OS and hardware makes VM less portable. Importing a VM still requires manual setup such storage, RAM and network.Highly portable since lightweight and zero dependency on hardware.Scalable and code-reusabilitySpinning up more VMs still need administrative tasks such as distributing resources to VM. Running a new machine puts extra load on the system resources also re-managing earlier VMs becomes a task. Every VM keeps its own copy of resources-poor code-reusability.Spinning up new docker containers simply means running pre-built images into containers as a process inside host OS. Containers are also configured on-the-fly passing parameters and run-time. Single image can be run and used to create many containers; encourage code-reusabilityResource utilizationStatic allocation results in resource wastage in case of idle VMs or if a VM’s resource requirement increases.Resources are dynamically allocated and de-allocated on the need basis by the docker engine.Docker system prune or garbage collectionVirtual machines do not have an in-built prune mechanism, these have to be administered manually.Docker image and containers can be pruned; which frees up a sensible amount of storage and memory space and CPU cycles.New environmentCreating new VM from the scratch is a tedious, repetitive tasks. It involves installing a new OS, loading kernel drivers and other tools and configurations.Package the code and dependency files, build into an image, run the image to create a new container. Use an existing or a base image (dockerhub- scratch) to run and create more containers on the go.Web-hosted HubNo web hosted hub for VMsdockerHub provides an open-source reliable trusted source of pre-built images that can be downloaded to run new containers.Version control (backup, restore,track history)(refer git)Snapshot of VMs are not very user-friendly and consume more space.Docker images are version controlled. Every delta difference in each docker container can easily be viewed (demo: docker diff ). Any change in the image is stored as a different layered version. A reference link to older images saves build time and space.Auto-buildAutomation of creating VMs is not very feasible.Docker images can also be auto-built from every source code check-in to GitHub (Automated builds on Dockerhub)Disaster recoveryTedious to recover from VM backup files.Easier to restore docker images (like files) just like git source files in case images are version controlled. Backup images only have to be run to create containers. (refer: screenshot).UpdateAll the VMs have to updated with the release patch.A single image is updated, re-built and distributed across multiple platforms.Memory usage+speedSlower: Entire snapshot of a machine and the OS is loaded into the cache memory.Real-time and fast: pre-built images. Only the instance, i.e, a container has to be run as a process and uses memory like an executableData integrityVM behavior may change if the dependency includes beyond the VM boundaries. (example: an app depends on production host network settings)Same behavior of apps in any environmentsecurityMore secure: A failure inside a VM may reach its guest OS but not the host OS or other virtual machines. Type-2 hypervisor though has a risk of kernel attack.Less secure: If a docker container compromised; underlying OS and hence all the containers may be affected since they share the same host kernel. OS Kernel may also be risked.Key providersRed hat KVM, VMWare, Oracle VM VirtualBox, Mircrosoft Hyper-V, Citrix XenServerDockers, Google kubernetes Engine, AWS Elastic Container serviceData authenticationLot of software licenses.Docker maintains inbuilt content trust to verify published images. When to use VM or a DockerWhen the need is an isolated OS, go for VMs.For a hardware and software independent isolated application that needs fast distribution on multiple environments, use dockers.Docker use-case:Example: A database application along with its databaseConsider the docker image - Oracle WebLogic Server on Docker Hub.This image is pre-built Oracle WebLogic Server runtime environment, including Oracle Linux 7 and Oracle JDK 8 for deploying Java EE applications.To create Server configurations on any machine, just download this image and run to create and start a container.There is no need to install and configure JDK, Linux or other run-time environment.Do not use Docker use-case:The application depends on utility outside the docker container.Code developed on dev machine with base OS as MAC; needs certain firewall setting on say Ubuntu OS.How can the code be tested on the production ubuntu OS firewall while running from MAC OS docker container?Solution: Install a virtualization software on host OS-MAC; Create a VM (Virtual machine) with host OS as Ubuntu (same as production environment).Configure the desired firewall settings on host VM – Ubuntu; import the test code inside Ubuntu and test.Use a VM:For Embedded systems programming, a VM is installed that connects to the system device drivers, controllers and kernel.Virtualization used along with docker:An extension to the previous scenario would be if you would want to also test your python application in the host OS-Ubuntu VM without having to set up the python exe and its libraries and binaries.All you have to do is: Install Docker engine for Ubuntu OS and pull the python image from Docker hub as:docker pull python:tag [ tag is the python version-choose the appropriate version ]docker pull python:2.7Refer: Python imageEither write a Dockerfile to import/copy entire source code to python environment or directly run the image passing the script path as below:Command:$docker run -it --name my-python-script -v “\$PWD”:/usr/src/myapp -w /usr/src/myapp python:2.7 python my-application.pyCommand options:-v = volume list-bind mount a volume [mount present working directory onto /usr/src/myapp inside container]-w = workdir string-working directory inside the containerMoreover; you can also test your python code in more than one version by downloading different python images, running them to create different containers and running your app in each container.What’s exciting here is that once the code tested in each python environment; you could quickly work on the test results and drop the containers. And deploy the code to production only once code tested against various python versions.Final thoughtsVMs and dockers are compatible with each other. Dockers are not here to replace Virtual machines.Both serve the same purpose of virtualizing the computing and infrastructure resources for optimized utilization.Using both Virtual machines and dockers together can yield better results in virtualization.When one desires a fast, lightweight, portable and highly scalable hardware-independent environment for multiple applications isolation; wherein security is not the major concern; Dockers is the best choice.Use a VM for embedded systems that are integrated with hardware; such as device driver or kernel coding.A scenario simulating an infrastructure setup with a high resource control and dependency on system resources; VMs are a better choice.Use of Dockers inside VMCI/CD pipelines scenario:Virtualization enables a smooth CI/CD process flow by promoting the users to concentrate only on developing the code on a working system that is set up for automated continuous integration and deployment without having to duplicate the entire setup each time.A virtualized environment is set up; either using a VM or a docker image that takes care of the automatic code check-ins, builds, regression testing, and deployments on the server.
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Docker Vs Virtual Machines(VMs)

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