Learn Alpine Linux - Container Runtimes: Docker & Podman

#Introduction

Alpine and containers are nearly identical twins: Alpine images are small, secure, and quick to pull. Episode 16 uses Alpine both as a container host and as a base image. You'll learn to install Docker, use the daemonless Podman, and build minimal images with multi-stage techniques.

After this episode, you'll be able to run and build containers on Alpine with two different runtimes, and understand why so many real-world Dockerfiles start with FROM alpine.

#Installing Docker on Alpine

#Docker with OpenRC

Docker is available in Alpine's community repository. Install and enable it:

apk add docker docker-cli-compose
rc-service docker start
rc-update add docker default
docker version

Explanation:

• docker-cli-compose provides the compose plugin.
• rc-update add docker default runs the daemon at boot.
• docker version verifies the client and server.

Run your first container:

docker run --rm alpine:latest echo "hello from alpine"
docker run -d -p 8080:80 --name web nginx
docker ps

docker run -d -p 8080:80 --name web nginx runs nginx on port 8080. Don't forget to open the port in the nft firewall from episode 10 if the container needs to be reachable from outside.

#Podman: Daemonless and Rootless

#An Alternative Without a Daemon

Podman offers command compatibility with Docker without a central daemon. Install and test it:

apk add podman
podman info
podman run --rm alpine:latest echo "hello from podman"

Podman's advantages:

• Daemonless: no big daemon process running.
• Rootless: regular users can run containers without doas.
• Supports systemd inside containers via podman run with certain options.

For regular users, set up rootless Podman:

adduser -G podman arman
podman system migrate

adduser -G podman arman adds the user to the podman group so they can manage containers.

#alpine:latest as the Base Image

#Why Alpine Is the Favorite Base

The alpine:latest image is only about 5 MB, making it the most popular base image in the container world. Look inside the image:

docker run --rm alpine:latest sh -c "cat /etc/alpine-release; apk --version"
docker images

To compare sizes, pull another distro's image:

docker pull debian:bookworm-slim
docker images | grep -E "alpine|debian"

The docker images output shows the striking size difference between alpine and debian-slim.

#Building Images with apk --no-cache

#A Minimal Dockerfile

Write a Dockerfile that installs packages with apk add --no-cache:

FROM alpine:latest
 
RUN apk add --no-cache nginx && \
    mkdir -p /run/nginx
 
COPY index.html /usr/share/nginx/html/
EXPOSE 80
 
CMD ["nginx", "-g", "daemon off;"]

apk add --no-cache prevents package index storage that would bloat the image. Build and run it:

docker build -t my-web .
docker run -d -p 8081:80 --name myweb my-web
curl -s http://localhost:8081/

The curl -s http://localhost:8081/ output shows the index page copied into the image.

#Multi-Stage Build

Multi-stage separates the build and runtime, producing a very small final image:

FROM golang:1.24-alpine AS builder
WORKDIR /src
COPY main.go .
RUN go build -o /app/app
 
FROM alpine:latest
COPY --from=builder /app/app /usr/local/bin/app
ENTRYPOINT ["app"]

COPY --from=builder /app/app /usr/local/bin/app only copies the built binary to the runtime stage, without the Go toolchain.

#Closing

Episode 16 ran containers on Alpine: installing Docker with OpenRC, using the daemonless and rootless Podman, understanding the advantages of the alpine:latest base image, and building images with apk --no-cache and multi-stage builds.

Key takeaways:

• Docker is installed with apk add docker and managed by OpenRC.
• Podman runs daemonless and supports rootless.
• alpine:latest is the most popular base image at about 5 MB.
• apk add --no-cache prevents the index from bloating the image.
• Multi-stage builds produce very small runtime images.
• Containers and Alpine reinforce each other: both are small and fast.

In the next episode, episode 17, we'll cover Alpine 3.24 and its newest features — what's new in the June 2026 release, Alpine 3.23's legacy of apk v3 and linux-stable, and how to upgrade between major versions safely.