Multi-container Pod
- Docker & Kubernetes course
- Intermediate
- Lesson 23/82
- 4 min
Learn to run multiple containers in a Pod.
Multi-container pods
Several containers are put in one pod only if they are tightly coupled. The most common pattern is the sidecar: a container helping the main application (log collector, proxy, syncer). They share files through a common emptyDir volume:
spec:
volumes:
- name: loglar
emptyDir: {}
containers:
- name: uygulama
image: api:1.0
volumeMounts:
- name: loglar
mountPath: /var/log/app
- name: log-gonderici
image: busybox:1.36
command: ["sh", "-c", "tail -F /loglar/app.log"]
volumeMounts:
- name: loglar
mountPath: /loglarInit containers
initContainers are containers that run in order and finish before the main containers. They are used to wait for a dependency to be ready or to prepare configuration files; the main containers don't start until all of them finish successfully:
spec:
initContainers:
- name: db-bekle
image: busybox:1.36
command: ["sh", "-c", "until nc -z db 5432; do sleep 2; done"]
containers:
- name: api
image: api:1.0For a specific container's log, kubectl logs api -c db-bekle is used.
Practice A pod with a sidecar
Write a pod YAML: name api; a loglar volume with emptyDir: {} under volumes; two containers: uygulama (api:1.0, mounts loglar at /var/log/app) and log-gonderici (busybox:1.36, mounts loglar at /loglar).
Starter code
# buraya yazSample solution
apiVersion: v1
kind: Pod
metadata:
name: api
spec:
volumes:
- name: loglar
emptyDir: {}
containers:
- name: uygulama
image: api:1.0
volumeMounts:
- name: loglar
mountPath: /var/log/app
- name: log-gonderici
image: busybox:1.36
volumeMounts:
- name: loglar
mountPath: /loglarExpected output
pod/api created NAME READY STATUS RESTARTS AGE api 2/2 Running 0 9s
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Should a web application and a database be put in the same pod?
- Only in production
- Only in Minikube
- No; they scale separately and have separate life cycles Correct answer
- Yes, always
Explanation: When a pod scales, all containers in it are copied together.
2 Show the log of a specific container in the pod.
kubectl logs api ____ db-beklekubectl logs api -c db-bekleExplanation: -c (container) selects the container name.
3 Match.
| Term | Meaning |
|---|---|
sidecar |
Helper container |
emptyDir |
Pod-lifetime shared directory |
initContainers |
Runs first and finishes |
-c |
Container selection |