How to Containerize Legacy Applications

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A legacy application is an old and popular piece of software. In the past, legacy applications were written for operating systems and hardware platforms. Legacy apps were Mainframe applications. However, it is an outdated application, and to run it, it should be converted into a newer and more efficient code using modern technologies and programming languages. There may be compatibility issues with Windows 10, but this program will run on Windows7. The development team of the vendor must support a third-party application it is running otherwise the operation team will find it difficult to operate the application. This means you should upgrade your hardware, coding language, and operating system.

What is a legacy app?

Legacy applications are widely used in factory computer systems, customer accounts in banks, air traffic control, and military defense installations. Furthermore, there is no need to update the software. Additionally, containerizing legacy applications would balance technical probability and business benefits. By containerizing legacy applications, they can be transformed into more efficient code. The operating system, the browser, and the IT system should be updated in comparison to recent software and technology. The migration of data and tools from older technologies to newer technologies is labor-intensive and involves migration of old data and tools to newer technologies. To migrate it, the IT chief information officer and the IT planner are responsible.

Drawbacks of the Legacy approach

A legacy system has uncountable problems like its excessive maintenance costs, data silos, lack of permission to governmental regulations, and reduced security. Such drawbacks are –

  1. Outdated: In the age of new technologies legacy applications are very outdated, slow, worse, and have less accuracy rate.
  2. Security: Insecurity matters outdated applications could be risky. It fails to protect from virus hacking. As legacy systems have large and inflexible nature it fails to correct the vulnerabilities.
  3. Investing in outdated technology is very expensive. Firms that make an initial investment into an outdated system are most likely to fix it or not alter it because they lack the funds.
  4. Exporting data from an old system with legacy technology is difficult and time-consuming. Even after importing it, the format of exported data can be difficult to migrate.
  5. In legacy system files, data formats are supported only to a certain extent. Legacy systems cannot handle formats that enlarge far beyond their capabilities. Affixed to them are businesses which suffer because of the limitation.
  6. Proprietary tools are not fun: Older systems are larger and dominions. They are difficult to change, adapt and customize.
  7. Meeting customers on their terms becomes impossible: Customers move with technology. This older system has problems with customer interaction. When customers find legacy problems they move ahead.

What is Containerization?

It is a form of the Operating system. Through this, applications run in isolated user spaces called containers, so it is an intermodal freight transport system that uses intermodal containers. In computing, containerization is the process of packaging software code, its dependencies, configuration, and other details so they can be opened within the same or another environment. Containerization is mainly used to package up many microservices into a single application. A container is an executable package of software that runs on top of a host operating system. It is possible for a host to support many containers. Technology is quickly supplanted and benefits developers and operations teams as well as software infrastructure.

How does Containerizing Legacy Applications help you?

By using the Statefulset resource, Kubernetes can coordinate sets and data persistence by providing a mechanism to track storage volumes and maintain hostnames after restarting the Container.. This allows Containerization of the parts of the legacy app that manages states such as Databases. It is important to ordain the efficiency advantage of container development for your application. Container software development companies should rebuild their organization to speculum the process of the new Container workflow.

  1. Container images maintain all the binaries, libraries, and dependencies, so environment-specific configuration can be ejected. The same image can now be viewed on multiple systems. By containerizing an application you would be able to isolate the file system and runtime from its host.
  2. Maintainability and scaling: It would be great if you make an architectural pattern in which a complex application forms small independent processes which communicate with each other through APIs. By resolving application conflicts between different environments, developers can impart their software and dependencies to IT operations and production environments.
  3. Container management tools: Legacy applications can take advantage of state-of-the-art orchestration frameworks such as Kubernetes. Third-party container management tools give mechanisms for networking, monitoring, and perseverance storage for containerized applications.

What is the Refactoring Approach?

Refactoring improves the internal structure of a program by preserving the source code. Code refactoring increases the objective quality of code that is linked to ease of maintenance. It helps to understand the code. It makes it easier to understand and comprehend the developers’ design decisions. Through the Refactoring process we can change the software system and improve its internal structure without changing the functionality of the code. Refactoring is part of the DevOps software development approach. In code refactoring, the main objective is to make the code more efficient and maintainable. There are many Refactoring factors- Red -Green Refactoring,

  • Preparatory Refactoring,
  • Branching by Abstraction Refactoring
  • Composing Methods Refactoring
  • User Interface Refactoring.

Refactoring makes downloads faster and updates easier. It improves the quality of existing code while maintaining its external behavior. Refactoring requires extracting software system structure, data models, and intra-application relationships. Refactoring activities produce architectural modification that weakens the structural architecture of a software system. Not only software code, but also hardware description languages have been refactored in recent weeks. These codes refactor in hardware description languages. The majority of Refactoring’s current tools were originally developed for Java. Refactoring plays an important role in application modernization.

What is Lift & Shift Approach?

Lift and Shift is an approach that allows you to move such applications (apps) from- premises to the Cloud. It is a fast, easiest, and budget-friendly process to migrate applications. As it permits the move of an exact copy of an application from one ambiance to another (from on-premises to public cloud), it is known as “rehosting”. Various companies recognize it as one of the most important processes. Applications are migrated using one of three cloud migration models: IaaS, PaaS, or SaaS.

As in the Lift and Shift approach, the management and security system is relatively easy to understand, so one can interpret the requirements to controls that should be implemented against compute, storage, and network resources. Even after the movement takes place, this approach allows the same architectural constructs. So, here it is significant that there are no definite changes required in terms of business processes that are related to the application as well as monitoring and management interfaces. Through the “Lift and Shift” technique a codebase is abstracted from one environment to another environment, without changing the design. For legacy migration projects it is exoteric. Like migration, it does not require effort.

How to Create a Plan to Develop a Suitable Container for Legacy Apps?

Containerization delivers developers to make an open application faster and more secure. When a developer transfers code from a desktop computer to a virtual machine, Containerization sorts out this problem by constructing the application code together with the related configuration files, libraries, and dependencies required to run. A ‘Container’ developed from an operating system can be used on any platform, including non-cloud platforms. For packaging our application and all its dependencies together in forms of containers, Docker is the containerization platform for deploying your application in any environment, be it development, test, or production.

How to Containerize a Legacy Application?

If you follow the below steps, you can migrate your legacy app into a container easily. Before I start migrating, let’s consider the legacy application is called ‘lagecy_file’.

Step 1: Break down the application

It would be easy to break down the application into three major divisions. These are, what service the ‘lagecy_file’ needs to run, which dependencies are going to use, and is it taking any persistent storage or not.

You need to use a separate container for external services. It helps to make the services easy to update and also allows multiple applications for overlapping services. Also, it is better to keep the data and the database in persistent storage individually.

Step 2. Creating a Reliable Base Image

Create a reliable base image for the ‘lagecy_file’ application. You have to select an image that is stable and maintained nicely. By defining a base image, it helps to connect and communicate with the host environment. Also, it helps to have a consistent build. Use a reliable set of libraries, dictionary structures, updated security patches, and dependencies to maintain the base image.

Step 3. Set up configuration

It is better to set the configuration at runtime while building the container. To define the configuration, you need to set logging and log storage, database location, storage, credentials, and access controls. Also, you need to configure your environment variable with each application. You can use different environment variables for testing and live applications.

Step 4. Add the application code

You need to change your application in order to add your application code. The ADD command allows you to include the code on your file. You need to specify the location of your application code, as well as where it should be stored.


A containerization process is a good way to complete legacy application migration easily. You can gain a lot of advantages from cloud infrastructure by containerizing your application. Providing standard and advanced technologies through containers is the right path for your company. No matter whether they’re moving to the cloud or not, containers are already a part of most IT hubs. With this article, we are striving to provide the best high-level guidance and knowledge. I hope this article helps you build a containerized legacy application. Now, do not waste more time and go and start containerizing your legacy application too.

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