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Pod status

Learn Pod status and phases.

Pod status

A pod's life cycle has phases:

  • Pending: accepted, not placed on a node yet or the image is being pulled.
  • Running: at least one container is running.
  • Succeeded: all containers finished successfully.
  • Failed: at least one container finished with an error.

The READY 1/1 column shows whether containers passed their readiness checks, and RESTARTS how many times they restarted.

NAME   READY   STATUS             RESTARTS      AGE
web    1/1     Running            0             5m
api    0/1     CrashLoopBackOff   4 (30s ago)   3m

Health checks

Kubernetes watches container health with probes:

  • livenessProbe: if it fails, the container is restarted (a hung application).
  • readinessProbe: while failing, the pod gets no traffic (not ready yet).
  • startupProbe: delays the other probes for slow-starting applications.
      readinessProbe:
        httpGet:
          path: /saglik
          port: 8080
        periodSeconds: 5
      livenessProbe:
        httpGet:
          path: /saglik
          port: 8080
        initialDelaySeconds: 10

Practice A container with probes

Write a pod YAML: name api; container named api, image api:1.0; readinessProbe checks the /saglik path on port 8080 with httpGet; livenessProbe uses the same path and port.

Starter code

terminal
# buraya yaz

Sample solution

terminal
apiVersion: v1
kind: Pod
metadata:
  name: api
spec:
  containers:
    - name: api
      image: api:1.0
      readinessProbe:
        httpGet:
          path: /saglik
          port: 8080
      livenessProbe:
        httpGet:
          path: /saglik
          port: 8080

Expected output

pod/api created

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 If STATUS is Running but READY is 0/1, what does it mean?

  • The pod was deleted
  • The image can't be pulled
  • Everything is fine
  • The container runs but fails its readiness check; it gets no traffic Correct answer

Explanation: A Service sends traffic only to ready pods.

2 Write the probe that restarts the container when it fails.

Question 
      ____:
        httpGet:
          path: /saglik
          port: 8080
Answer 
      livenessProbe:
        httpGet:
          path: /saglik
          port: 8080

Explanation: readinessProbe doesn't restart; it only cuts the traffic.

3 Match.

Term Meaning
Pending Waiting to be placed
Succeeded Finished successfully
livenessProbe Restart when hung
readinessProbe No traffic if not ready

All lessons in Intermediate

1 What is Kubernetes?

  1. What is Kubernetes?
  2. Why Kubernetes?
  3. Cluster architecture
  4. Control plane
  5. Worker node
  6. Summary - What is Kubernetes

2 Minikube

  1. What is Minikube?
  2. Installing Minikube
  3. minikube start
  4. minikube status
  5. minikube dashboard
  6. Summary - Minikube

3 kubectl basics

  1. What is kubectl?
  2. kubectl get
  3. kubectl describe
  4. kubectl apply
  5. kubectl delete
  6. Summary - kubectl

4 Pod

  1. What is a Pod?
  2. Pod YAML
  3. Creating a Pod
  4. Pod status
  5. Multi-container Pod
  6. Summary - Pod

5 Deployment

  1. What is a Deployment?
  2. Deployment YAML
  3. Replica count
  4. Rolling update
  5. Rollback
  6. Summary - Deployment

6 ReplicaSet

  1. What is a ReplicaSet?
  2. ReplicaSet YAML
  3. ReplicaSet selector
  4. Scaling
  5. Self-healing
  6. Summary - ReplicaSet

7 Service

  1. What is a Service?
  2. ClusterIP
  3. NodePort
  4. LoadBalancer
  5. Service selector
  6. Summary - Service

8 ConfigMap

  1. What is a ConfigMap?
  2. ConfigMap YAML
  3. Environment variable
  4. Mounting as a volume
  5. kubectl create configmap
  6. Summary - ConfigMap

9 Secret

  1. What is a Secret?
  2. Secret types
  3. Secret YAML
  4. Mounting a Secret
  5. kubectl create secret
  6. Summary - Secret

10 Namespace

  1. What is a Namespace?
  2. kubectl get namespaces
  3. Creating a Namespace
  4. The -n flag
  5. Default Namespace
  6. Summary - Namespace

11 Labels and selectors

  1. What is a label?
  2. Adding labels
  3. Label selector
  4. kubectl get -l
  5. Equality and set selectors
  6. Summary - Labels

12 Project: Multi-tier app

  1. Project design
  2. Database Deployment
  3. Web Deployment
  4. ConfigMap and Secret
  5. Putting it together - multi-tier

13 Troubleshooting

  1. kubectl logs
  2. kubectl exec
  3. kubectl describe pod
  4. CrashLoopBackOff
  5. Pending Pod
  6. Summary - Troubleshooting

14 Intermediate final

  1. Challenge - Pod YAML
  2. Challenge - Deployment
  3. Challenge - Service
  4. Challenge - ConfigMap
  5. Challenge - Intermediate project