Beyond Docker: Exploring Modern Container Engines and Build Tools

Why Move Away from Docker?

If you have used Docker for a long time, convincing you to consider alternatives requires solid reasons. Docker is a monolithic tool that tries to cover every function, which is rarely the best practice; specialized tools that excel at a single task often outperform it.

All the tools discussed adhere to the OCI (Open Container Initiative) specifications, so switching does not mean learning new concepts—CLI commands and APIs remain compatible.

Container Engines

Docker’s main competitor is Red Hat’s Podman , which runs without a daemon and does not require root privileges. Podman also manages pods, the smallest compute unit in Kubernetes, making migration to Kubernetes easier.

Example of running two containers in a pod:

~ $ podman pod create --name mypod
~ $ podman pod list

POD ID   NAME   STATUS   CREATED          # OF CONTAINERS   INFRA ID
211eaecd307b   mypod   Running   2 minutes ago   1   a901868616a5

~ $ podman run -d --pod mypod nginx   # First container
~ $ podman run -d --pod mypod nginx   # Second container
~ $ podman ps -a --pod

CONTAINER ID   IMAGE                         COMMAND   CREATED       STATUS   PORTS   NAMES          POD           POD NAME
3b27d9eaa35c   docker.io/library/nginx:latest   nginx -g daemon ...   2 seconds ago   Up 1 second ago   brave_ritchie   211eaecd307b   mypod
...

Podman’s CLI mirrors Docker’s, so an alias docker=podman works seamlessly.

Other engines include:

LXD – a daemon‑based Linux container manager offering system‑container capabilities, more VM‑like.

CRI‑O – a Kubernetes‑focused runtime, not intended for direct end‑user use.

rkt – a now‑defunct engine from CoreOS, kept for completeness.

Image Builders

While Docker remains popular for building images, several alternatives exist.

Buildah (Red Hat) works hand‑in‑hand with Podman; podman build is essentially a Buildah wrapper. It supports Dockerfile/Containerfile, runs root‑less, and offers fine‑grained layer control.

Example Buildah workflow:

~ $ buildah bud -f Dockerfile .
~ $ buildah from alpine:latest   # Create base container
~ $ buildah run alpine-working-container -- apk add --no-cache python3
~ $ buildah commit alpine-working-container my-final-image
~ $ buildah images
REPOSITORY          TAG     IMAGE ID        CREATED        SIZE
localhost/my-final-image latest 1ff90ec2e26   22 seconds ago 51.4 MB

Kaniko builds images from Dockerfiles inside Kubernetes clusters without a daemon, useful for CI/CD pipelines.

BuildKit (next‑gen Docker build) offers parallel builds, cache, and root‑less options but still requires a daemon.

Additional niche builders:

S2I – builds images directly from source code, popular on OpenShift.

Jib – Java‑focused image builder with Maven/Gradle plugins.

Bazel – a full build system that can also produce container images via rules_docker.

Container Runtimes

The runtime executes containers. Most users need not change it unless they have specific performance or security requirements.

runC – the default OCI‑compliant runtime used by Docker, Podman, and CRI‑O.

Crun – a Red Hat C‑based runtime, faster and more memory‑efficient than runC.

CRI‑O – a Kubernetes‑only runtime that internally uses runC.

containerd – a CNCF graduated project, daemon for managing images and runtimes, used by Docker Engine and many Kubernetes services.

Image Inspection and Distribution

Skopeo (Red Hat) inspects images and copies them between remote registries without pulling them locally.

Dive analyses image layers for efficiency, providing readable output useful in CI pipelines.

Conclusion

The goal is not to force you to abandon Docker, but to present the full landscape of tools for building, running, managing, and distributing containers. Each tool has strengths and trade‑offs; evaluating the combination that best matches your workflow and scenario is the key takeaway.