Immutable Infrastructure

What is Immutable Infrastructure?

With the rise of cloud services, immutable infrastructure is also witnessing popularity. Immutable infrastructure means servers that are never modified after the deployment because they work differently. If you want to update any existing server you can’t make those changes as the main goal of deploying an immutable infrastructure is to keep the server intact. In case if you still want to update the server or replace it with a new version or update, fix, or modify it, you can try these things:

  • You can build a new server from a common image using appropriate changes, packages, and services included.
  • You can also provide a new server to replace the existing one.
  • You can demobilize the old server.

If you apply any of these changes, you can still roll back the previous environment as the previous images are still available. The best part of this is, it almost removes the process for troubleshooting for any broken instances and makes new servers ready to deploy by using OS-level virtualization.

Immutable infrastructure Vs. Mutable Infrastructure

Immutable Infrastructure

Mutable Infrastructure

It lets you track and rollback changes easily. Whenever a new server or virtual machine is deployed, IT teams can see it.

To provision servers, more time is needed because the manual configuration is a must.

As there is consistency in the configuration between the servers, testing seems easy.

Because of a variety of unexpected reasons like connectivity, unresponsive repos, DNS offline, update failures are very common.

Since the infrastructure is never modified, IT teams see fewer complexities.

Diagnosing server issues is difficult because each server has a unique configuration (also known as configuration drift).

It supports DevOps, Cloud computing, virtualization, or the scenarios where the number of interdependent elements is high.

It can’t support DevOps or Cloud computing as debugging is complex due to an unanticipated state.

It ensures almost zero configuration drift because no changes are made in the server.

Configuration drift is common as changes to the server are not documented, which makes version tracking even more difficult.

Benefits of Immutable Infrastructure

  • Minimum Support Calls: Organizations that rely on immutable infrastructure receive a lower number of support calls and even if the calls appear they can be resolved easily by deleting those instances that create problems. Engineers can also track the root cause of failure to eliminate it.
  • Improves Security: Organizations face challenges to determine the distinction between normal operation and an exception. However, immutable infrastructure really helps such organizations to spot distinction and at the same time help them. By using machine learning, exceptions can easily be identified and it can also replace manual rules. With immutable infrastructure, you can prevent some exceptions before appearing.
  • Takes Advantage of Whitelisting for Security: It enhances security by implementing whitelisting. For example, rules can be applied to an application that should not consume a specified amount of memory by applying whitelisting rules. It ceases the security breaches in real-time and makes security personnel aware of the possible attack. Whitelisting is also helpful to deploy applications securely.
  • Mitigates Configuration Drift: When you don’t know whether all your servers have the same configuration, troubleshooting servers becomes a tedious task. It happens because multiple instances of the server run at the same time. And to correct it you need to employ a person who can configure the server manually. Still, it’s a chaotic way to configure servers. But when you use immutable infrastructure the only time you need to check the configuration is before the deployment of the server.
  • Avoids Synchronization: If you update instances while they are running there can be lots of problems with security and configuration. However, to deal with such situations you need continuous synchronization. Continuous synchronization consistently updates the configuration changes that have been made since the last update. Although this process can lead to some misconfigured servers, which is also a security threat. But immutable infrastructure eliminates the need for synchronization and also deals with such security threats.
  • Benefits from Cloud Capabilities: The cloud platform helps remove or create virtual machines on the fly, and this feature supports immutable infrastructures. These platforms work in a way that they don't disturb applications, and even if there is a need to switch traffic between instances, they stop all the instances until the running transactions are completed.
  • Ensures Fast Recoveries: When DevOps teams deploy new instances they also save the old instances just to ensure that whenever the rollback is required it should be seamless and quick. Also, it enables development teams to look at the working of the older versions.
  • Brings Experimentation: Any technology that facilitates an easy way of experimenting, the teams love it. Immutable infrastructure ensures that experimenting is easy and safe as the feature of rollback drives out the fear of experimenting tension and also paves the way for innovation.

Scenarios where Immutable Infrastructure can be used:

  • Large Scale Infrastructure Management: Configuration drift is a reality and it increases as time passes by. However, to deal with or to counter drift, you can’t apply configuration but you need to be able to rebuild infrastructure components periodically. For example, Microsoft destroys and rebuilds servers every month using Azure, which is not possible without immutable infrastructure.

    Servers have the tendency to fail any time and after a certain scaling point, they should be replaced. And this problem is applied to hardware and software as well. Since immutable infrastructure can replace or rebuild field components at a rapid pace, they can be used to scale as well. Immutable infrastructure is better as it eases the process of replacement of physical devices as well as the latest configuration. Once the latest configuration is out you can replace it with the old one.
  • Change Management: Any organization when encounters the situation of change management, needs a person who has the answers to the many questions. In such instances, things can get difficult. For example, you need a reliable testing strategy to counter a state where you meet up with inconsistent results. However, if you have an immutable infrastructure at your side and once you change or make changes to the networking devices or they do not show the exact result as expected, you can rollback the configuration to a last successful configuration.

Immutable Server Best Practices

If you can build and test server images quickly, you can take full advantage of immutable servers.

Here are some ways that will help you to do so:

  • Build Images on chroot: Running installation and update tools in a chroot jail can help you make changes to it as a static directory structure. The Packer amazon-chroot builder can do this for AWS AMI images.
  • Reduce Test Expand: Automated test suites can become heavy and take more time in the future. To avoid this, ensure to keep tests ducked and fast-running so they don’t overwhelm the change process.
  • Cache Installation Files: If the time needed to run updates and installation on the server image is high, teams must find ways to optimize it. One way is to cache the source files closer to where the image is built. It means mirroring package repositories, using caching proxies, or moving in-house software repositories to a closer location on the network or cloud.
  • Layer Images: To reduce the time needed to update servers is to use multiple layers of images. For example, a base server image could have the OS, with all of the packages installed and updated. New images can be created starting with this base image, so only the newest changes need to be applied. The base image may be updated from time to time, especially when OS packages and other common files are released.
  • Minimize the OS Image: The time needed to boot server instances and save server images, increases with the size of the OS installation. So teams can optimize the process by stripping the base OS down to the bare minimum files and packages required for their use case. This has many added benefits, including reducing the surface area for security attacks and lowering the time to boot servers for automated scaling and recovery.
  • Use Containers for Quick Results: Containers can change the dynamic of immutable infrastructure dramatically. Often, applications are packaged into a container image and promoted through a pipeline. This process follows the immutable configuration model, as a new image is built whenever any of the files or configuration in the container is changed. And it is quicker to build and deliver a container image than a full server image.

Best Tools to Setup Immutable Infrastructure:

There are many tools available for configuration management, automation, and containerization, but not all of them will help you set up an immutable infrastructure. To smoothen the process for you, we’ve listed down the best tools for immutable infrastructure:

  • Packer: You can create multiple machine images using a single source configuration.
  • Terraform: It helps you manage change within your deployment stack while maintaining Infrastructure as a Code.
  • Docker: It is used to create and manage images and separate application services.
  • Docker Swarm: It scales up the power of Docker by creating a cluster of Docker hosts.
  • SaltStack: It is a configuration management tool that helps you control a number of microservers from a single master server.
  • Jenkins: It is an open-source automation tool that helps you create pipelines for build, test, and deploy.


The reason why immutable infrastructure gaining popularity is that it can speed up the deployment process. However, people still doubt this claim. But the reality is: it does increase the performance, though, rarely the actual performance on an individual server can be slower than a mutable server. With an immutable server, horizontal scaling is easier as it supports quicker environment building, with both more machines and speedier deployments.