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Introduction

While Docker remains a popular choice, several powerful alternatives have emerged, each solving specific challenges like security, performance, and automation. Tools like Podman, containerd, Buildah, RunC, and platforms like OpenShift offer unique advantages tailored to modern container workflows.

The container landscape has changed a fair bit since Docker changed the way we packaged and deployed applications. While Docker is still one of the most widely used options today, some compelling alternatives are well worth considering that might better fit your needs. Let me share my journey to explore these alternatives and what I've learned along the way.

The Evolution of Container Runtimes

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When Docker first came into this world, that was the technology that was able to collect in one tool functions of container creation and managing with runtime. This was somewhat revolutionary, but then with time, as usage for containers matured, it became evident that teams needed particular tools for particular aspects in containerization, and that is what led to alternative specialization.

Understanding Container Standards

The container ecosystem is based on open standards - most notably the [Open Container Initiative (OCI)]. That standardizes:

This standardization means you are not being locked into any particular tool. You can build your images in one tool and run them in another. This gives you the choice to utilize the best tool to get a particular job done.

Podman: The Daemon-free Alternative

In the intensity of working as a DevOps engineer with the container, I have found Podman to be a game-changer in teams that take the security aspect seriously-that means avoiding root privileges. It's daemonless compared with Docker, which is a big architectural change. Daemonless approach just magically changes how teams do container security in production environments.

Security through Designs

The first time I had switched to Podman for a security-conscious client, this daemonless architecture made total sense. Each container runs with your user permissions - not as a privileged daemon:

Running a container as your user
podman run nginx  # No root, no daemon

# Even rootless containers can bind to privileged ports
podman run -p 80:80 nginx   # Works without root!

Kubernetes-like Experience on Desktop

But what was a really pleasant surprise was the pod-native support in Podman. It allows trying out Kubernetes-like concepts on a local system:

# Create a pod with multi containers
podman pod create --name my-app 
podman run --pod my-app -d nginx
podman run --pod my-app -d redis

containerd: The Kubernetes Runtime

Having operated large Kubernetes clusters, one learns to love the focused approach of containerd. A light-weight, high-performance container runtime, it powers a lot of container platforms, including indirectly, Kubernetes. From my experience, containerd really does one thing and does it well: it runs containers efficiently.

Platform Building

This focus of containerd shines when looking at building container platforms:

// Simple integration with containerd
client, err := containerd.New("/run/containerd/containerd.sock")
container, err := client.NewContainer(ctx, "nginx",
containerd.WithNewSnapshot("nginx", image),
containerd.WithNewSpec(oci.WithImageConfig(image))

Interactive Decision Helper

Not sure which alternative fits your needs? Try this interactive tool:

Container Engine Finder

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Performance Requirements

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BuildKit: Reimagining Container Building

I remember when container builds were slow and not really efficient, and were usually a bottleneck of our CI/CD pipelines. That is until I discovered BuildKit and my life changed. BuildKit is the next-generation builder engine for Docker, but it can also be used independently.

Concurrent and Efficient Builds

The best thing about BuildKit is how it parallelizes the steps of building:

# These stages build concurrently
FROM golang:1.21 AS backend
COPY backend. 
RUN go build

FROM node:18 AS frontend
COPY frontend. 
RUN npm build

FROM alpine 
COPY --from=backend /app/backend.  
COPY --from=frontend /app/dist ./dist

LXC/LXD: System Containers

Working with legacy applications that needed full system access taught me that a different way to do containerization is by using LXC/LXD. The focus in system containers, rather than application containers, can be thought of like a light VM rather than what most consider the typical container.

Development Environments

LXD does great at isolated development environments:

# Create a full Ubuntu environment
lxc launch ubuntu:20.04 dev-env
lxc exec dev-env -- sudo apt install python3

# Share your project folder
lxc config device add dev-env code disk source=/path/to/code path=/code

Buildah: Creating Containers Without a Daemon

Buildah is a lightweight tool I often use to build OCI-compliant images, without needing a container daemon like Docker. It’s perfect for scripting, automation, and CI/CD workflows, especially when you want a clean, minimal setup.

Why I Prefer Buildah:

• Daemonless Operation: No container runtime daemon is required.
• Automation-Friendly: Works seamlessly in shell scripts and CI/CD pipelines.
• OCI-Compliant: Compatible with Podman, containerd, and other tools.

Example: Creating an Image with Buildah

Here’s a quick workflow to show how simple it is:

# Start with an empty image
buildah from scratch  

# Add a file to the image
buildah run my-container -- touch /hello.txt  

# Commit the changes to a new image
buildah commit my-container my-custom-image:latest  

When I use Buildah:

• Lightweight, daemonless image builds for CI/CD pipelines.
• Scripts or environments where Docker isn’t an option.
• Cleaner builds in restricted environments.

RunC: Minimal and Efficient Container Runtime

RunC is my go-to when I need a lightweight, low-level container runtime. It’s the reference implementation of the OCI runtime spec and powers tools like Docker and containerd. It does exactly one thing: runs containers—no frills like networking or orchestration, which makes it incredibly fast and efficient.

Example: Getting Started with RunC

Here’s what I do to set it up:

# Generate a container spec:
runc spec  

# Run the container:
sudo    runc run my-container  

When I choose RunC:

• Custom runtime scenarios.
• Lightweight execution with minimal dependencies.
• Full control over container operations.

Red Hat OpenShift: A Developer-Friendly Kubernetes Platform

If you’re using Kubernetes but need something more streamlined for teams, OpenShift is a solid choice. It’s built on Kubernetes but adds developer-focused tools, automation, and security enhancements to simplify workflows.

Why OpenShift Stands Out:

• Built-in Developer Tools: CI/CD pipelines, Source-to-Image (S2I), and a user-friendly web console.
• Enterprise-Grade Security: Stronger security defaults compared to plain Kubernetes.
• Kubernetes-Compatible: Apps remain compatible with vanilla Kubernetes.

Example: Deploying an App with OpenShift

Here’s a typical deployment process:

# Log in to the cluster
oc login <cluster-url>  

# Create a new project
oc new-project my-app  

# Deploy an application
oc new-app --name=myapp python:3.9~https://github.com/username/repo.git  

# Expose the app with a route
oc expose svc/myapp  

Feature Comparison Table

Feature	Docker	Podman	containerd	Buildah	RunC	LXC/LXD	OpenShift
Best For	General Use	Security	Kubernetes	Image Builds	Lightweight	System Containers	Enterprise Kubernetes
Daemonless	No	Yes	Partial	Yes	Yes	No	No
OCI Compatible	Yes	Yes	Yes	Yes	Yes	Partial	Yes
Ease of Use	High	Easy	Medium	Medium	Low	Medium	High
Developer Tools	Advanced	Basic	Limited	Limited	None	Limited	Advanced
Rootless Support	No	Yes	Partial	Yes	Yes	No	No
Focus Area	All-in-One	Local Dev	Performance	CI/CD Builds	Container Execution	Full Systems	DevOps + Security
Integration	Broad	Kubernetes	Kubernetes	Podman/OCI	Custom	OS-level	Kubernetes Ecosystem
Resource Overhead	Medium	Low	Low	Low	Lowest	Medium	Medium
Multi-container	Yes	Yes	Yes	No	No	Yes	Yes

Conclusion

Through my journey of exploring alternatives to Docker, it has been learned that the container ecosystem is a lot more to do with selecting the right tool for your needs opposed to finding a perfect replacement. Podman's rootless approach brings security without sacrifice, Containerd's simplicity lends itself perfectly in Kubernetes environments, BuildKit transforms how we build images, and LXC/LXD offers a unique take on system containerization.

The cool thing about modern container tools is in the way they interoperate: You can have efficient builds with BuildKit, run them with Podman in development, and deploy to Containerd in production. This flexibility, enabled by OCI standards, lets us create workflows that truly fit our needs rather than adapting our needs to fit a single tool.