World K2: Trays & Orders

Sidecars and init containers

You will learn: how to run a prep step before your app, and a helper beside it all day.

Checked with Kubernetes 1.37 on 31 Oct 2026

The problem

Your web server crashes at start. The menu file is not there yet. Something must lay it out first, then step aside. Who should do it?

Watch

You are here: cluster kind-dev namespace default

~/shop $ kubectl apply -f kedai.yamlpod/kedai created~/shop $ sleep 2~/shop $ kubectl get pod kedaiNAME    READY   STATUS     RESTARTS   AGEkedai   0/2     Init:0/2   0          2s~/shop $ sleep 10~/shop $ kubectl get pod kedaiNAME    READY   STATUS    RESTARTS   AGEkedai   2/2     Running   0          12s

An is the prep cook. It runs first, finishes, then leaves. Init:0/2 means 0 of 2 init containers are done. The web server waits for them.

Try it

How does the kedai tray start and stop? Put the steps in order.

First step at the top. Put these in order. Use the arrows, or drag.

prep lays out the menu, then exits
sweeper stops last
Closing time: web stops first
web starts serving
sweeper starts and keeps running

Watch

A is a helper who stays all day, like a log shipper. It sits under initContainers. Which of its lines makes sweeper stay all day?

Try it

Your turn. Apply kedai.yaml. Watch STATUS change until READY says 2/2.

You are here: cluster kind-dev namespace default

dev-control-planeOpenManager

No trays here.

dev-workerOpen

No trays here.

dev-worker2Open

No trays here.

Time: +0s (sped up)

Hint

Type kubectl apply -f kedai.yaml, then kubectl get pods a few times.

Predict

In noprep.yaml, the prep cook exits with an error. What does kubectl get pods show?

Check

You are here: cluster kind-dev namespace default

~/shop $ kubectl apply -f noprep.yamlpod/noprep created~/shop $ sleep 6~/shop $ kubectl get pod noprepNAME     READY   STATUS                  RESTARTS     AGEnoprep   0/1     Init:CrashLoopBackOff   1 (3s ago)   6s~/shop $ kubectl logs noprep -c prepwhere is the menu file

Real error: Init:CrashLoopBackOff. Plain words: the prep step keeps failing, so the tray never opens. Read its logs with -c prep.

You did it!

You can now add a prep step and an all-day helper to a pod.

Go deeper (optional)

Native sidecars are stable since Kubernetes 1.33. Older guides put helpers under containers:. Then a Job never finishes while its helper runs. A native sidecar does not hold a Job open.

Real rep (optional): on a throwaway cluster, apply kedai.yaml and watch it with kubectl get pod kedai -w.