Learn Kubernetes Basics

Tasks

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Tasks
Install Tools
Install and Set Up kubectl
Install Minikube
Administer a Cluster
Administration with kubeadm
Certificate Management with kubeadm
Upgrading kubeadm clusters from v1.11 to v1.12
Upgrading kubeadm clusters from v1.12 to v1.13
Upgrading kubeadm clusters from v1.13 to v1.14
Upgrading kubeadm HA clusters from v1.11 to v1.12
Upgrading kubeadm HA clusters from v1.12 to v1.13
Manage Memory, CPU, and API Resources
Configure Default Memory Requests and Limits for a Namespace
Configure Default CPU Requests and Limits for a Namespace
Configure Minimum and Maximum Memory Constraints for a Namespace
Configure Minimum and Maximum CPU Constraints for a Namespace
Configure Memory and CPU Quotas for a Namespace
Configure a Pod Quota for a Namespace
Install a Network Policy Provider
Use Calico for NetworkPolicy
Use Cilium for NetworkPolicy
Use Kube-router for NetworkPolicy
Romana for NetworkPolicy
Weave Net for NetworkPolicy
Access Clusters Using the Kubernetes API
Access Services Running on Clusters
Advertise Extended Resources for a Node
Autoscale the DNS Service in a Cluster
Change the default StorageClass
Change the Reclaim Policy of a PersistentVolume
Cluster Management
Configure Multiple Schedulers
Configure Out Of Resource Handling
Configure Quotas for API Objects
Control CPU Management Policies on the Node
Customizing DNS Service
Debugging DNS Resolution
Declare Network Policy
Developing Cloud Controller Manager
Encrypting Secret Data at Rest
Guaranteed Scheduling For Critical Add-On Pods
IP Masquerade Agent User Guide
Kubernetes Cloud Controller Manager
Limit Storage Consumption
Namespaces Walkthrough
Operating etcd clusters for Kubernetes
Reconfigure a Node's Kubelet in a Live Cluster
Reserve Compute Resources for System Daemons
Safely Drain a Node while Respecting the PodDisruptionBudget
Securing a Cluster
Set Kubelet parameters via a config file
Set up High-Availability Kubernetes Masters
Share a Cluster with Namespaces
Static Pods
Using a KMS provider for data encryption
Using CoreDNS for Service Discovery
Using sysctls in a Kubernetes Cluster
Configure Pods and Containers
Assign Memory Resources to Containers and Pods
Assign CPU Resources to Containers and Pods
Configure GMSA for Windows pods and containers
Configure Quality of Service for Pods
Assign Extended Resources to a Container
Configure a Pod to Use a Volume for Storage
Configure a Pod to Use a PersistentVolume for Storage
Configure a Pod to Use a Projected Volume for Storage
Configure a Security Context for a Pod or Container
Configure Service Accounts for Pods
Pull an Image from a Private Registry
Configure Liveness and Readiness Probes
Assign Pods to Nodes
Configure Pod Initialization
Attach Handlers to Container Lifecycle Events
Configure a Pod to Use a ConfigMap
Share Process Namespace between Containers in a Pod
Translate a Docker Compose File to Kubernetes Resources
Manage Kubernetes Objects
Declarative Management of Kubernetes Objects Using Configuration Files
Declarative Management of Kubernetes Objects Using Kustomize
Managing Kubernetes Objects Using Imperative Commands
Imperative Management of Kubernetes Objects Using Configuration Files
Inject Data Into Applications
Define a Command and Arguments for a Container
Define Environment Variables for a Container
Expose Pod Information to Containers Through Environment Variables
Expose Pod Information to Containers Through Files
Distribute Credentials Securely Using Secrets
Inject Information into Pods Using a PodPreset
Run Applications
Run a Stateless Application Using a Deployment
Run a Single-Instance Stateful Application
Run a Replicated Stateful Application
Update API Objects in Place Using kubectl patch
Scale a StatefulSet
Delete a StatefulSet
Force Delete StatefulSet Pods
Perform Rolling Update Using a Replication Controller
Horizontal Pod Autoscaler
Horizontal Pod Autoscaler Walkthrough
Specifying a Disruption Budget for your Application
Run Jobs
Running Automated Tasks with a CronJob
Parallel Processing using Expansions
Coarse Parallel Processing Using a Work Queue
Fine Parallel Processing Using a Work Queue
Access Applications in a Cluster
Web UI (Dashboard)
Accessing Clusters
Configure Access to Multiple Clusters
Use Port Forwarding to Access Applications in a Cluster
Use a Service to Access an Application in a Cluster
Connect a Front End to a Back End Using a Service
Create an External Load Balancer
Configure Your Cloud Provider's Firewalls
List All Container Images Running in a Cluster
Set up Ingress on Minikube with the NGINX Ingress Controller
Communicate Between Containers in the Same Pod Using a Shared Volume
Configure DNS for a Cluster
Monitoring, Logging, and Debugging
Application Introspection and Debugging
Auditing
Debug a StatefulSet
Debug Init Containers
Debug Pods and ReplicationControllers
Debug Services
Debugging Kubernetes nodes with crictl
Determine the Reason for Pod Failure
Developing and debugging services locally
Events in Stackdriver
Get a Shell to a Running Container
Logging Using Elasticsearch and Kibana
Logging Using Stackdriver
Monitor Node Health
Resource metrics pipeline
Tools for Monitoring Resources
Troubleshoot Applications
Troubleshoot Clusters
Troubleshooting
Extend Kubernetes
Configure the Aggregation Layer
Use Custom Resources
Extend the Kubernetes API with CustomResourceDefinitions
Versions of CustomResourceDefinitions
Setup an Extension API Server
Use an HTTP Proxy to Access the Kubernetes API
TLS
Certificate Rotation
Manage TLS Certificates in a Cluster
Federation
Set up Cluster Federation with Kubefed
Set up CoreDNS as DNS provider for Cluster Federation
Set up placement policies in Federation
Cross-cluster Service Discovery using Federated Services
Administer Federation Control Plane
Federated Cluster
Federated ConfigMap
Federated DaemonSet
Federated Deployment
Federated Events
Federated Horizontal Pod Autoscalers (HPA)
Federated Ingress
Federated Jobs
Federated Namespaces
Federated ReplicaSets
Federated Secrets
Manage Cluster Daemons
Perform a Rolling Update on a DaemonSet
Perform a Rollback on a DaemonSet
Install Service Catalog
Install Service Catalog using Helm
Install Service Catalog using SC
Extend kubectl with plugins
Manage HugePages
Schedule GPUs

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Determine the Reason for Pod Failure

This page shows how to write and read a Container termination message.

Termination messages provide a way for containers to write information about fatal events to a location where it can be easily retrieved and surfaced by tools like dashboards and monitoring software. In most cases, information that you put in a termination message should also be written to the general Kubernetes logs.

Before you begin

You need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster. If you do not already have a cluster, you can create one by using Minikube, or you can use one of these Kubernetes playgrounds:

To check the version, enter kubectl version.

Writing and reading a termination message

In this exercise, you create a Pod that runs one container. The configuration file specifies a command that runs when the container starts.

debug/termination.yaml 
apiVersion: v1
kind: Pod
metadata:
  name: termination-demo
spec:
  containers:
  - name: termination-demo-container
    image: debian
    command: ["/bin/sh"]
    args: ["-c", "sleep 10 && echo Sleep expired > /dev/termination-log"]

  1. Create a Pod based on the YAML configuration file:

    kubectl apply -f https://k8s.io/examples/debug/termination.yaml

    In the YAML file, in the cmd and args fields, you can see that the container sleeps for 10 seconds and then writes “Sleep expired” to the /dev/termination-log file. After the container writes the “Sleep expired” message, it terminates.

  2. Display information about the Pod:

    kubectl get pod termination-demo

    Repeat the preceding command until the Pod is no longer running.

  3. Display detailed information about the Pod:

    kubectl get pod termination-demo --output=yaml

    The output includes the “Sleep expired” message:

    apiVersion: v1
kind: Pod
...
    lastState:
      terminated:
        containerID: ...
        exitCode: 0
        finishedAt: ...
        message: |
          Sleep expired
        ...

  4. Use a Go template to filter the output so that it includes only the termination message:

    kubectl get pod termination-demo -o go-template="{{range .status.containerStatuses}}{{.lastState.terminated.message}}{{end}}"

Customizing the termination message

Kubernetes retrieves termination messages from the termination message file specified in the terminationMessagePath field of a Container, which as a default value of /dev/termination-log. By customizing this field, you can tell Kubernetes to use a different file. Kubernetes use the contents from the specified file to populate the Container’s status message on both success and failure.

In the following example, the container writes termination messages to /tmp/my-log for Kubernetes to retrieve:

apiVersion: v1
kind: Pod
metadata:
  name: msg-path-demo
spec:
  containers:
  - name: msg-path-demo-container
    image: debian
    terminationMessagePath: "/tmp/my-log"

Moreover, users can set the terminationMessagePolicy field of a Container for further customization. This field defaults to “File” which means the termination messages are retrieved only from the termination message file. By setting the terminationMessagePolicy to “FallbackToLogsOnError”, you can tell Kubernetes to use the last chunk of container log output if the termination message file is empty and the container exited with an error. The log output is limited to 2048 bytes or 80 lines, whichever is smaller.

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