From Docker Build to Kubernetes Deploy on Ubuntu: The Image Workflow That Never Changed

Amid all the noise about dockershim, one thing got lost: the everyday workflow of building an image with Docker and running it on Kubernetes never changed. Docker is still an excellent build tool, Kubernetes still runs OCI images, and on Ubuntu the loop is clean. Here it is end to end. 1. A build-friendly Dockerfile Multi-stage keeps the runtime image small and the attack surface low — this matters more on Kubernetes, where you pull the image onto every node that schedules the pod: # build stage FROM golang:1.22 AS build WORKDIR /src COPY go.* ./ RUN go mod download COPY . . RUN CGO_ENABLED = 0 go build -o /out/api ./cmd/api # runtime stage — distroless, no shell, tiny FROM gcr.io/distroless/static:nonroot COPY --from=build /out/api /api USER nonroot:nonroot EXPOSE 8080 ENTRYPOINT ["/api"] 2. Build and push with Docker on Ubuntu Use buildx (bundled with modern Docker) so you can build multi-arch — worth it if any nodes are arm64: docker buildx build \ --platform linux/amd64,linux/arm64 \ -t registry.example.com/api:1.4.2 \ --push . Tag with an immutable version, never rely on :latest . Kubernetes caches images per node; :latest makes "which build is actually running?" unanswerable and breaks rollbacks. 3. A deployment that behaves in production apiVersion : apps/v1 kind : Deployment metadata : name : api spec : replicas : 3 selector : { matchLabels : { app : api } } template : metadata : { labels : { app : api } } spec : containers : - name : api image : registry.example.com/api:1.4.2 # the exact tag you pushed imagePullPolicy : IfNotPresent ports : [{ containerPort : 8080 }] resources : requests : { cpu : " 100m" , memory : " 128Mi" } limits : { memory : " 256Mi" } readinessProbe : httpGet : { path : /healthz , port : 8080 } initialDelaySeconds : 3 livenessProbe : httpGet : { path : /healthz , port : 8080 } initialDelaySeconds : 10 The readinessProbe is the piece people skip and regret: without it, Kubernetes sends traffic to a pod before your app is listening, and