Containerization tools in 2026: Docker (the default, daemon-based, rootful), Podman (daemonless, rootless, drop-in Docker replacement), nerdctl (Docker-compatible CLI for containerd, used by Kubernetes nodes), BuildKit (the new build engine, also used by Docker and Podman), and img (the unprivileged alternative for immutable infrastructure). The right pick: Docker for most teams, Podman if you need rootless or daemonless, BuildKit for advanced build features.
Table of contents
- The 5 tools at a glance
- Docker vs Podman: the real difference
- The BuildKit advantage
- rootless containers with Podman
- Picking the right tool
- How this fits the rest of the stack
- FAQ
The 5 tools at a glance
Docker - the default. dockerd daemon, docker CLI, Moby project upstream. The team that has been using Docker for years keeps using it; the team that starts fresh can also pick Docker and not be wrong.
Podman - the daemonless alternative. podman CLI, no daemon, rootless by default. Drop-in Docker replacement (the docker alias works). The team that needs rootless or hates the daemon uses Podman.
nerdctl - Docker-compatible CLI for containerd (the runtime Kubernetes uses). nerdctl run, nerdctl build, same flags as Docker. The team that has containerd but wants the Docker CLI experience uses nerdctl.
BuildKit - the new build engine, used by Docker 23.0+ and Podman. Concurrent builds, better caching, multi-platform. The team that builds many images or has slow Docker builds uses BuildKit.
img - the unprivileged, daemonless build tool from Jessie Frazelle. The team that needs to build images without root and without a daemon uses img.
Docker vs Podman: the real difference
Architecture: Docker has a central daemon (dockerd) that runs as root. Every docker CLI command talks to the daemon. Podman has no daemon - each command is a process, fork-exec model.
Rootless: Docker requires root for the daemon. Podman is rootless by default - the user namespace is mapped, the container runs as the user. The team that needs rootless (multi-tenant CI, security-sensitive workloads) uses Podman.
Docker Compose: Docker has Compose built in. Podman has podman-compose (a separate tool) and supports Compose v3 with caveats. The team that uses Compose heavily should verify Podman compatibility before switching.
BuildKit: Both Docker and Podman use BuildKit as the build engine. The Dockerfile syntax is identical; the build cache and parallelism differ. The team that uses BuildKit features (multi-stage caching, secrets) gets the same on both.
Compatibility: Podman is mostly drop-in for Docker. The same Dockerfile, the same image, the same container. The team that switches to Podman does not rewrite their Dockerfiles.
The BuildKit advantage
BuildKit replaced the legacy builder in Docker 23.0+ and is the default in Podman. The advantages:
-
Concurrent builds - multiple
docker buildcommands run in parallel. -
Better caching - per-stage caching, content-addressable cache, distributed cache (registry, S3).
-
Multi-platform builds - build for linux/amd64, linux/arm64, etc. in one command:
docker buildx build --platform linux/amd64,linux/arm64 . -
Build secrets - mount secrets at build time without leaving them in the image:
docker buildx build --secret id=mysecret,src=./secret.txt .
The team that has slow Docker builds (over 5 minutes) usually gets a 2-5x speedup with BuildKit features enabled.
rootless containers with Podman
Podman runs rootless by default:
podman run -d -p 8080:80 nginx
The container’s UID 0 (root) maps to the host user’s UID. The container cannot see the host’s root filesystem. The team that runs multi-tenant CI (multiple users building images on the same host) uses rootless Podman for safety.
Docker can do rootless too, but it requires manual setup (rootlesskit, slirp4netns). The team that wants rootless with the least friction uses Podman.
Picking the right tool
Default pick: Docker. Mature, integrated, huge community, every CI tool supports it. The team that does not have a specific reason to pick something else picks Docker.
Need rootless: Podman. Daemonless, rootless by default, drop-in for Docker. The team that has a multi-tenant CI or a security-sensitive workload picks Podman.
Building on Kubernetes nodes: nerdctl. The same CLI as Docker, the same images, but uses containerd (the runtime Kubernetes uses). The team that wants Docker ergonomics on a K8s node uses nerdctl.
Need faster builds: BuildKit. Concurrent, cached, multi-platform. The team that has slow Docker builds enables BuildKit features.
Need an unprivileged build tool: img. The team that builds in CI without root uses img.
FAQ
Is Podman a drop-in replacement for Docker?
Mostly. The CLI is the same, the Dockerfile is the same, the images are the same. The exceptions: Docker Compose works differently, Docker Swarm has no Podman equivalent, Docker Desktop features (Extensions, Dev Environments) are Docker-only. The team that uses docker run, docker build, docker ps can switch to Podman without rewriting.
Why would I use Podman over Docker?
Rootless by default, no daemon, less attack surface. The team that runs in a security-sensitive environment, or that runs multi-tenant CI, or that has hit Docker daemon issues, uses Podman.
What is the difference between Docker and containerd?
containerd is a container runtime (the layer that actually runs containers). Docker is a higher-level tool that uses containerd underneath (since Docker 23.0+). The team that runs Kubernetes uses containerd directly via kubelet; the team that uses Docker Desktop uses containerd via Docker.
Can I use Docker Compose with Podman?
Yes - podman-compose is a separate tool that reads docker-compose.yml files. The team that uses Compose heavily should verify podman-compose supports the features they use (most v3 features work, some v2 networking features do not).
Should I use buildx?
Yes if you have Docker 23.0+ (buildx is included). The team that needs multi-platform builds, build secrets, or just faster builds uses docker buildx build instead of docker build.
How this fits the rest of the stack
For a sense of what the full project costs before it commits, the RunxBuild hosting calculator shows the line items together. The API, the database, the storage, the worker, the bandwidth - each one is a separate number, and the team’s mental model for the platform is the sum of those numbers.
Useful related references: