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10 Best Docker Alternatives 2021

Docker is a popular open source platform for developing, testing, deploying, and managing applications. Notably, Docker features a virtual production environment known as container that can be easily shared with others.

However, some developers complained about challenges associated with using Docker containers during their app development process.

Popular Docker alternatives have capitalized on some of these challenges to create virtualized platforms with features lacking in Docker.

In this article, I will show you the 10 best Docker alternatives that are ideal for creating a virtual isolated environment for app development and offer users unique benefits that make them stand out.

Why Do You Need A Docker Alternative?

Docker has advanced the programming environment by launching the Docker virtual platform for app development. Its software container is flexible, light with not much demand on system resources, and easy to deploy.

To ensure constant development and update of its programs, Docker made its programs open-source and also partners with major programming communities worldwide.

Nonetheless, Docker is the leading player in virtualized platform developments, but as I earlier pointed out, it has its lapses, which are enough reasons to seek alternative virtualized platforms.

Having been well familiar with running Docker and other alternatives, I have outlined reasons why Docker alternatives might be the best option for you.

The Docker daemon will not run if you don’t grant it root privileges. This is one challenge addressed by RedHat’s Daemonless Podman, which lets you run containers without root privileges.

Managing data stored on Docker’s containers might be difficult since all data held in a container is wiped off when you shut down the container. To prevent this, you might have to save the data on a container to a different location.

Although Docker addressed this issue, developers still experience difficulty in storing data on the Docker platform.

Selecting a suitable Docker alternative from the list of ten best alternatives I will be presenting will significantly depend on what suits your need as a developer.

Without further ado, let me reveal the best Docker alternatives.

10 Best Docker Alternatives 2021

1. Podman

The first Docker alternative on our list is Podman.

Podman is an open-source, alternative virtualization platform by RedHat. Like Docker, you can use the Podman container engine to develop, manage, and run OCI containers on Linux machines. However, Podman Container Engine runs on a daemonless architecture that does not require root privileges.

With Podman, containers are run in the background without root privileges because it integrates directly with systemD (system daemon), which allows it to run in the background. Hence, the system takes over the Docker daemon functionality in Podman.

Running Podman, a daemonless container engine, gives you a considerable advantage security-wise since a container relies on user privileges. This adds an extra layer of protection by making daemonless containers less prone to attacks because any attack on the container has to be done by the user since the container is running under user privileges.

However, running Podman on your machine will require that you install additional features that will allow rootless containers to run on user namespaces. Hence, you might enjoy more features on Podman.

Another reason you might consider Podman is its integration with other developer tools. Podman enjoys wider integration with developer tools than Docker, which offers you a compatible API that makes switching possible.

In summary, Podman is a better option security-wise. Because it enjoys a higher degree of compatibility; therefore, you can easily switch from Docker or other container engines to Podman since Podman is OCI-compliant with support for Docker files and images.

2. OpenVZ

Another Docker alternative on our list is OpenVZ.

OpenVZ from Virtuozzo is a Linux-based containerization technology similar to Docker in terms of features and functionalities, but with the capacity to do more than just application deployment.

OpenVZ allows users to create several isolated Linux containers on a Linux server. Consequently, these Linux-based containers are used to create isolated environments for hosting Virtual servers (e.g., most Virtual Private Servers deployed in VPN technology are hosted in OpenVZ containers).

In this case, each container acts as a standalone server with independent root access, memory, IP address, system libraries, applications, and files. This ability prevents applications run in VZ containers from conflicting and also enables each application to be initiated independently.

OpenVZ’s Network File System (NFS) is an important feature associated mainly with OpenVZ. This feature allows users to access network disk files from virtual servers hosted on OpenVZ.

Therefore, as a system or network administrator, you can use the NFS to move or share virtual servers between two or more physical servers since the NFS supports real-time migrations for IA64 processors.

In summary, OpenVZ is a powerful virtual platform for hosting containers while also serving as hypervisors for hosting virtual servers for offering distributed cloud storage, dedicated support, management tools, and other functionalities.

3. VirtualBox

VirtualBox, initially released in 2007, is similar in functionality to Docker since they are both virtual platforms that developers can use to create and run applications. However, unlike Docker, developers can use VirtualBox to create several virtual machines running on different operating systems.

This makes it favorable for apps that require a different OS to run. Also, since VirtualBox runs on X86 and AMD64/Intel64 OS, it allows easy storage and backup of files to cloud-based storage facilities and also switches between Operating Systems without the rigors of storing data in containers on Docker.

Security-wise, VirtualBox offers more robust features since virtual machines created on VirtualBox do not share the host’s Operating System kernel. This is unlike containers in Docker, which faces more security risks by sharing the host’s Operating System kernel.

In summary, VirtualBox may not be as portable as Docker or other Docker alternatives. Still, it offers users the benefits of running any OS type on a single machine, running Graphics-based applications smoothly, easy sharing of files and folders, cross-platform support, and a more secure virtual environment without requiring hardware virtualization.

Like Docker, VirtualBox runs on open-source code under the GNU General Public License version 2 (GPL v2).

4. Kubernetes (K8)

Unlike other best Docker Alternatives on our list, Kubernetes is a popular one.

Kubernetes (aka K8) is an open-source container automation system developed by Google to manage container applications in physical, virtual, or cloud environments. Kubernetes functions as an orchestrator that controls thousands of containers and workloads.

If you’re running multiple containerized applications irrespective of their hosting platforms, you will be needing Kubernetes, which serves as an API for coordinating, controlling, scheduling, and automating multiple containers.

Although Docker performs a similar orchestration function, unlike Kubernetes, it can only manage a node (made of a cluster of containers), and it does not have an automatic node rescheduling feature for rescheduling inactive nodes.

In contrast, Kubernetes can easily and efficiently manage multiple clusters (multiple nodes) and automatically reschedule inactive nodes.

If you’re running multiple containerized applications, you can combine Docker with Kubernetes. Kubernetes lets you manage and control multiple containers from a single machine and helps you network, do load-balancing, and security upscaling across all your container nodes.

If you’re worried about granting group privileges, Kubernetes uses a built-in isolation mechanism much like namespaces to group containers based on root privileges.

This functionality allows developers to collaborate successfully on projects without the complexity associated with managing multiple container applications and resources.

In summary, Kubernetes gives you control over large clusters of containers and users interacting together. It allows interaction between containers and users, balances loads efficiently, makes it easy to handle security and authentication at the infrastructure level, and manages synchronization between multi-platform containerized environments.

5. LXC (Linux Containers)

LXC is a Linux-based containerization engine that enables users to create multiple isolated Linux environments on a single Linux machine. Unlike Docker, LXC acts as a hypervisor for creating multiple Linux machines with separate system files, networking features, and applications.

Although Linux’s LXC is an older containerization technology abandoned for Docker, it made a strong comeback by building on Docker’s shortcomings which include reduced disk performance, poor volume management, and sharing host resources such as IP address, system files, hostname, etc.

Docker and LXC are the most preferred of the several containerization engines available because both Docker and LXC are lightweight and can be easily deployed. However, LXC can function as an alternative to hypervisors and it is much preferred for data-intensive applications and operations.

In summary, LXC is lighter than Docker, uses fewer system resources, provides more security options, acts as a VM, supports ‘Copy-On-Write’, and allows users to create independent network interfaces.

If you prefer a lightweight container engine that is also a better alternative to traditional hypervisors and preferable for data-intensive applications, then LXC will make a better choice.

6. Microsoft Azure Container Registry

Microsoft Azure Container Registry is a private Docker registry for storing and managing container images using DCLI (Docker Command Line Interface) tools. It offers users much more robust security options, including container vulnerability scanning, runtime protection, and compatibility with Twist Lock.

Microsoft Azure lets developers migrate easily from Monolithic architecture to containerized environments. It also makes container management easy without requiring expertise. This makes Microsoft Azure a more robust option for managing container clusters, and it allows developers to run and scale apps easily by using Kubernetes, Docker Swarm, and other container orchestrators.

Microsoft AZC works much like Docker Hub by serving as a catalog of container images, granting users direct control of container contents, enabling integrated authentication, supporting geo-replication of services such as virtual network configuration using a private link, tag locking, etc.

In summary, Microsoft Azure Container Registry provides users with the benefit of deploying containerized applications from the Azure platform to other virtual platforms using third-party tools like Docker Enterprise Edition and OpenShift.

Users also enjoy powerful visual studio tools for debugging and deploying containerized applications, easy sharing of container images to authenticated Microsoft Azure Container Registries, and flexibility in deploying container services, including container scaling.

Therefore, Microsoft Azure provides a much more robust virtualization platform compatible with Docker and other containerized services.

7. Containerd

Containerd is another entry on our list of the best Docker alternatives.

Containerd is a standalone container runtime that incorporates simplicity, robustness, and portability at the core of its operations. Containerd was formerly a tool that runs as part of Docker container services until Docker decided to graduate its components into standalone components.

Interestingly, on February 28, 2019, Containerd became a standalone component, and now a project in the Cloud Native Computing Foundation, placing it in the same class with popular container tools like Kubernetes, Prometheus, and CoreDNS.

Users can install Containerd without installing Docker since it can run alone using runc as a low-level container runtime. You can opt for high-level runtime like kata-runtime, depending on your needs. When users install Docker, it automatically installs Containerd, which runs the Kubernetes Container Runtime Interface (CRI) using its CRI plugin.

Running Containers on Docker gives you the advantage of upgrading and rebooting the Docker daemon without having to shut down or restart containers. Therefore, Containerd’s API gives you total control, making it easier to manage containers in a virtual environment.

Running Docker installs Containerd automatically, but Containerd can standalone as a high-level container runtime that does not require Docker to function.

In summary, Containerd acts as a client layer on which platforms like Kubernetes, Docker, etc., can build on without worrying about the Host Kernel.

Therefore, with Containerd, you enjoy the push and pull functionality, container creation management, and execution using Image management APIs, Snapshot management, and many more features without worrying about the Host Operating System.

8. Rancher

Rancher is a high-level orchestration software for managing container clusters. Usually, when administrators manage multiple clusters, it becomes challenging to administer such large groups of clusters, each with a unique configuration and access control settings.

Rancher makes managing a complex environment much easier using automation. For example, in a large organization, each department may have a cluster. Managing the whole cluster as a group manually becomes challenging, especially if the administrator has to revoke a user’s rights spread across multiple clusters in an organization.

With Rancher, the administrator can remove the user from all groups of clusters where he may have access rights at once using Rancher, making the process faster and error-free.

Unlike other top Docker alternatives, Rancher is ideal for managing groups of orchestration engines like Docker Swarm and Kubernetes, which makes it a virtualization solution deployed on a large scale.

In summary, Rancher is a powerful technology that helps users to manage and automate all cluster processes created by Kubernetes or Docker Swarm. Hence, Rancher, Docker Swarm, and Docker can be used at different levels since they are designed for different functionalities.

Therefore, corporations deploying Rancher enjoy the advantages of having a production-ready Kubernetes platform, either on-prem or Kubernetes as a Service, reduced overhead management, application catalog, automated deployment, etc.

9. Vagrant

HashiCorp Vagrant is a tool for replicating multiple conditioned virtual environments across multiple virtual machines and Operating Systems.

Vagrant is used for setting up a virtual environment that can be replicated multiple times across different networks, virtual machines, and OS to avoid the ‘works on my computer’ situation since Vagrant can create identical virtual environments for app staging, production, and deployment.

With Vagrant, you can create images of virtual machines and share them with your teammates across multiple platforms to create virtual environments with the same compilers and libraries. This differs from Docker, which often resets to the old image when it is restarted.

Vagrant runs on all major virtualization platforms like VirtualBox, VMware, or cloud platforms and offers users the highest levels of isolation available on the physical device it is running on.

Unlike Docker with isolation at the user level, Vagrant offers users separate features and functionalities that can be used together.

Overall, Vagrant is used for creating singular workflow environments on virtual machines to give users the advantages of automation, reduced setup time, and increased productivity, thus eliminating the ‘works on my computer’ scenario.

10. ZeroVM

Last but not the least on our handpicked list of the best Docker alternatives, we have ZeroVM.

ZeroVM is an open-source, lightweight virtualization technology based on Google’s Chromium Native Client (NaCl) project. With ZeroVM, users can create a secure and isolated environment for embedding applications.

Unlike other virtualization platforms that virtualize the whole system, ZeroVM virtualizes at the application level by embedding an application in an isolated environment, giving it an advantage of faster deployment.

Running ZeroVM prevents attackers from accessing application data since such an application is embedded in an isolated environment, which makes it suitable for applications or processes running unverified or untrusted code in multiple virtual environments.

ZeroVM is unique from hypervisors and container technologies because it can isolate single processes at the application level without needing an OS or kernel, which gives it the fastest startup time, less than 6 milliseconds.

Overall, ZeroVM offers developers a highly secured isolated virtual environment at the application level and fast startup time since it does not run at the operating system level, making it deployable for application processes in multiple virtual environments.

Wrapping Up – What Is The Best Docker Alternative?

Any of the ten best Docker alternatives will serve as a better alternative to Docker since each entry above addresses specific virtualization needs or shortfalls associated with Docker.

Therefore, the best alternative depends on users’ specific needs or features lacking in Docker, which makes it difficult to declare a specific alternative as the best.

However, if you seek an alternative with similar Docker features and functionality that works great without Root privileges, Podman is the perfect option to consider.

On the other hand, OpenVZ will make the best pick for users that require a virtualization engine with the hybrid functionality of a hypervisor and a container engine.

Nevertheless, all of the ten best Docker alternatives discussed above are free. However, you may have to pay affordable fees for premium services depending on your choice of Docker alternative.