Blogs

Kubernetes Objects

 

Node

 

List all nodes in the cluster

kubectl get nodes

Delete a node from the cluster

kubectl delete node <node name>

Show the metrics of a node

kubectl top node <node name>

Describe a node in detail

kubectl describe node <node name>

List all pods in a namespace, with more details

kubectl get node -o wide ¬-n <namespace>

Add an annotation to a node

kubectl annotate node <node name> 

Add a label to given node

kubectl label node <node name> type=label

Show node labels

kubectl get nodes --show-labels

Show information about a node in yaml format

kubectl get node <node name> -o yaml

Show information about a node with the given label

kubectl get node --selector=<label>

 

Pod

 

List all the pods in a namespace

kubectl get pod -n <namespace>

List pods with more details

kubectl get pods -o wide

Show the detailed description of pod

kubectl describe pod <pod name>

Delete a pod with a file describing it

kubectl delete -f pod.yaml

Create a pod in a certain namespace

kubectl create pod <pod name> -n <namespace>

Create a pod from an image

kubectl run <pod name> --image=<image name>

Show logs of a pod

kubectl logs <pod name> -n <namespace>

Execute a command in a pod and get an interactive terminal

kubectl exec -it <pod name> -- <command>

List all running pods in a namespace

kubectl get pods --field-selector=status.phase=Running

Live monitor the state of a pod

kubectl get pod <pod name> --watch

Live monitor the state of all pod

kubectl get pod -A --watch

Show all pods in json format

kubectl get pods -o json

List all pods in all namespaces

kubectl get pods --all-namespaces

List all pods in all namespaces

kubectl get pods -A

Show metrics for a given pod

kubectl top pod <pod name>

Show metrics for a given pod and all its containers

kubectl top pod <pod name> --containers

View container logs of a pod (if it has more than one container)

kubectl logs <pod name> -c <container name>

Get the documentation for the pod manifest

kubectl explain pod

List pods with labels

kubectl get pods --show-labels

kubectl using a different kubeconfig

kubectl --kubeconfig=<path to config file> get pods

Get the initContainer status of a pod

kubectl get pod --template '{{.status.initContainerStatuses}}' <pod name>

Print a list of pods sorted by name

kubectl get pods --sort-by=.metadata.name

 

Deployment 

 

Create a new deployment

kubectl create deployment <deployment name> --image=<image>

Create a new deployment from a manifest file

kubectl apply -f <deployment manifest>

List deployments

kubectl get deployment <deployment name>

Watch a specific deployment

kubectl get deployment <deployment name> --watch

List all deployments

kubectl get deployment -A

Show the detailed state of a deployment

kubectl describe deployment <deployment name>

Delete a deployment

kubectl delete deployment <deployment name>

Rolling update nginx of deployment

kubectl set image deployment/<deployment name> <container name>=<image>

Scale a deployment to 10 instances

kubectl scale --replicas=10 deployment/<deployment name>

Autoscale a deployment to stay near 80% cpu usage with the limitation of staying between 10-15 instances

kubectl autoscale deployment/<deployment name> --min=10 --max=15 --cpu-percent=80

Rolling back to the previous revision

kubectl rollout undo deployment/<deployment name>

Rolling back to a specific revision

kubectl rollout undo deployment/<deployment name> --to-revision=<revision name>

Check the rollout status of a deployment

kubectl rollout status deployment/<deployment name>

Show the revision history of a deployment

kubectl rollout history deployment/<deployment name>

Live edit a deployment

kubectl edit deployment/<deployment name>

Port forwarding of a deployment to a specific port

kubectl port-forward deployment/<pod name> <localhost port>:<pod port>

 

DeamonSets

 

List all the daemon sets in a namespace

kubectl get daemonset --namespace <namespace>

List all daemon sets in all namespaces

kubectl get daemonset --all-namespaces

Detailed information about a daemonset in yaml format

kubectl get daemonset <daemonset name> --namespace <namespace> -o yaml

Detailed information for a specific daemon set in a namespace

kubectl describe daemonset <daemonset  name> --namespace <namespace>

 

Configmaps

 

Create configmap from a file

kubectl create configmap <configmap name> --from-file <configmap manifest>

Get more details about specific configmap

kubectl describe configmap <configmap name>

List all configmaps in a namespace

kubectl get configmap --namespace <namespace>

Get specific configmap in yaml format

kubectl get configmap <configmap name> -o yaml

List all configmaps in all namespaces in yaml format

kubectl get configmap --all-namespaces -o yaml

 

Services

 

List all services in a namespace

kubectl get services  --namespace <namespace>

List the services in a namespace with additional information

kubcetl get service --namespace <namespace> -o wide

Show the detailed information of a service

kubectl describe service <service name>

Delete a particular service

kubectl delete service <service  name>

Get the documentation for service manifests

kubectl explain service

Port forwarding a service

kubectl port-forward service/<service name> <localhost port>:<service-port> 

Creates a Service of type nodeport with a mapping of post 8080 to 80

kubectl create service nodeport <service name> --tcp=8080:80

List services with their labels

kubect l get service --show-labels

Describe a service in yaml format

kubect l get service <service name> -o yaml

 

Service Account

 

List Service Accounts

kubectl get serviceaccounts

Detailed state of a service accounts

kubectl describe serviceaccount <serviceaccount name>

Replace a service account

kubectl replace serviceaccount <serviceaccount name>

Delete a service account

kubectl delete serviceaccount <serviceaccount name>

Live edit a service account

kubectl edit serviceaccount <serviceaccount name>

 

Secrets

kubectl describe secret/<secret name>

 

Show all secrets in a namespace

kubectl get secrets -n <namespace>

Describe a secret in more details

kubectl describe secret/<secret name>

List secrets in all namespaces

kubectl get secrets --all-namespaces

List secret in yaml format

kubectl get secret <secret name> -o yaml

 

Roles

 

List all roles in cluster

kubectl get roles --all-namespaces

List all clusterroles

kubectl get clusterroles

List all role bindings and clusterrolebindungs in the cluster

kubectl get (cluster)rolebinding --all-namespaces

Create the role “pod-reader” which can list and watch pods

kubectl create role pod-reader --verb=get --verb=list --verb=watch --resource=pods

 

Namespace

 

Create a namespace

kubectl create namespace <namespace name>

List all namespaces in a cluster

kubectl get namespaces

Get a namespace description in yaml format

kubectl get namespace <namespace name> -o yaml

Display detailed state of a namespace

kubectl describe namespace <namespace name>

Delete a namespace

kubectl delete namespace <namespace name>

Edit and update the definition of a namespace

kubectl edit namespace <namespace name>

Create a namespace using a yaml file

kubectl create -f namespace.yaml	Create a namespace using a yaml file

 

Replicasets

 

List all replicasets in current namespace

kubectl get replicasets

Describe detailed a replicaset in detail

kubectl describe replicaset <replicaset name>

List ReplicaSets with more information

kubectl get replicaset -o wide

List ReplicaSet in yaml format

kubectl get replicaset <replicaset name> -o yaml

Get the documentation for the ReplicaSet manifest

kubectl explain replicaset

List all persistent volumes in a namespace

kubectl get persistantvolume -n <namespace>

Describe a persistent volume

kubectl describe persistantvolume <persistantvolume name>

Delete a persistent volume

kubectl delete persistantvolume < persistantvolume name>

List the storage classes in yaml format

kubectl get storageclass –o yaml 

 

PersistentVolume Claim

 

List all persistent volume claims in a namespace

kubectl get persistentvolumeclaim <persistentvolumeclaim  name>

Describe a persistent volume claim

kubectl describe persistentvolumeclaim <persistentvolumeclaim name>

Delete a persistent volume claim

kubectl delete persistentvolumeclaim <persistentvolumeclaim name>

List ingress resource

kubectl get ingress

List ingress resources in all namespaces

kubectl get ingress --all-namespaces

Get information about the ingress object

kubectl explain ingress

Get information about an ingress

kubectl describe ingress <ingress  name>

List all ingress objects with their corresponding services

kubectl get ingress -o=custom-columns='NAME:.metadata.name,SVCs:..service.name'

 

Labels

 

List assigned labels on the node

kubectl get nodes --show-labels

List assigned labels on the pods

kubectl get pods --show-labels

Add label to node

kubectl label nodes <node name> <label>

Remove label from a node, same command but you see minus after the label name

kubectl label node <node name> <label>-

Set to the pod the label status and value unhealthy, overwriting any existing value

kubectl label --overwrite pods <pod name> status=unhealthy

 

Events

 

View all events in the cluster

kubectl get events --all-namespaces

List events in json format

kubectl get events -o json

Get events from of a pod

kubectl get events | grep <pod name>

This also shows events

kubectl describe pod <pod name>

List Events sorted by timestamp

kubectl get events --sort-by=.metadata.creationTimestamp

List all warning events

kubectl events --types=Warning

 

API Resources

 

Enumerates the resource types available

kubectl api-resources

List api group

kubectl api-versions

All namespaced resources

kubectl api-resources --namespaced=true

All non-namespaced resources

kubectl api-resources --namespaced=false

List all CRDs

kubectl get crd

List storageclasses

kubectl get storageclass

List the “healty” status of components

kubectl get componentstatuses

 

Themes

Logs & Conf files

 

Config folder

/etc/kubernetes/

Certificate files

/etc/kubernetes/pki/

Credentials to API server

/etc/kubernetes/kubelet.conf

Superuser credentials

/etc/kubernetes/admin.conf

kubectl config file

~/.kube/config

Kubernets working dir

/var/lib/kubelet/

Docker working dir

/var/lib/docker/, /var/log/containers/

Etcd working dir

/var/lib/etcd/

Network cni

/etc/cni/net.d/

Log files

/var/log/pods/

log in worker node

/var/log/kubelet.log, /var/log/kube-proxy.log

log in master node

kube-apiserver.log, kube-scheduler.log, kube-controller-manager.log

 

Quotas & limits

 

List Resource Quota

kubectl get resourcequota

List Limit Range

kubectl get limitrange

Customize the resource limit of a pod for CPU

kubectl set resources deployment nginx -c=nginx --limits=cpu=200m

Customize the resource limit of a pod for memory

kubectl set resources deployment nginx -c=nginx --limits=memory=512Mi

 

Annotations & Taints

 

Get annotations of deployment

kubectl describe deployment/<deployment name> | grep Annotations

Update annotations

kubectl annotate pods <pod name> <key>=<value>

Override annotation of a resource

kubectl annotate --overwrite <resource type> <resource name> <key>=<value>

Update the taints of a nodes

kubectl taint <node name> <taint name>

 

Common Metric Commands

 

Show metrics for a given node

kubectl top node <node name>

Show metrics for a given pod

kubectl top pod <pod name>

Show metrics for a given pod and all its containers

kubectl top pod <pod name> --containers

 

Common Log commands

 

Check logs of a pod

kubectl logs <pod name> --namespace <namespace>

Container logs in a pod (if more than one)

kubectl logs <pod name> <container name>

Logs from all containers in a pod

kubectl logs <pod name> --all-containers

Get logs from the last hour

kubectl logs --since=1h <pod name>

Display the most recent 20 lines of logs

kubectl logs --tail=20 <pod name>

Save the logs into a file 

kubectl logs <pod name> <file name>

Get logs filtered by label

kubectl logs -l <label key>=<label value> --all-containers

Get logs from deployment

kubectl logs deployment/<deployment name>

Get logs from job

kubectl logs job/<job name>

Export logs to a file

kubectl logs <pod name> > <file name>

 

Security

 

List Network Policy

kubectl get networkpolicy

List certificates

kubectl get certificate

Show kubeconfig settings

kubectl config view

Get a List of contexts

kubectl config get-contexts

Display current context

kubectl config current-context

Set default context to <cluster name>

kubectl config use-context <cluster name>

Set namespace field for context

kubectl config set-context <context name> --namespace=<namespace>

Set cluster field for context

kubectl config set-context <context name> --cluster=<cluster name>

Set user field for context

kubectl config set-context <context name> --user=<username>

 

Maintenace

 

Mark the named node as unschedulable

kubectl cordon <node name>

Mark the named node as schedulable

kubectl uncordon <node name>

Drain the node in preparation for maintenance

kubectl drain <node name>

This will give you the pod CIDR addresses for each of the nodes in your cluster.

kubectl get nodes -o jsonpath='{.items[*].spec.podCIDR}'

Delete a resource matching a label

kubectl delete <resource type> -l <label key>=<label value>

Display addresses of master / services

kubectl cluster-info

Detailed info about the cluster state to stout

kubectl cluster-info dump

This will show pod network CIDR which used by kube-proxy

kubectl cluster-info dump | grep -m 1 cluster-cidr

Dump current cluster state to a given file

kubectl cluster-info dump --output-directory=/path/clusterinfo.txt

To get all objects of your cluster

kubectl get all --all-namespaces 

List services, pods, nodes, deployments and replicasets

kubectl get svc, po, no, deploy, rs

Output yaml to a file, creating template

kubectl run <pod name> --image=nginx --dry-run=client -o yaml > pod1.yaml

 

Addendum: Docker

Install on Linux

 

Install docker in linux terminal

curl -sSL https://get.docker.com/ | sh

Install add. utils for docker (on RedHat systems)

sudo yum install -y yum-utils

Install docker

sudo yum install docker-ce docker-ce-cli containerd.io

Start docker engine

sudo systemctl start docker

Check status of docker

systemctl status docker

Get information about the docker installation

docker info

 

Container management

 

Create a container

docker create <image name>

Create a container and run it

docker run <image name>

Starting the given container

docker start <container name>

Stopping the given container (graceful)

docker stop <container name>

Restart (stop + start) the given container

docker restart <container name>

Kill the given container (SIGKILL)

docker kill <container name>

Pause the given container

docker pause <container name>

Resume the given container

docker unpause <container name>

Remove the container

docker rm <container name>

Force the removal of running container

docker rm -f <container name>

Real-time events from the given container

docker events <container-name>

 

Image management:

 

View docker images on local machine

docker images

Check running container

docker ps

Check all containers (running and stopped)

docker ps -a

Run the given container in background

docker run -d <container name>

Delete the container with the ID

docker rm <container id>

Show image history

docker history <image id>

Tag an image

docker tag <source image> <target image>

Delete an image

docker rmi <image name>

Get low-level information

docker inspect <image name>

 

Images

 

Pull an image from a Registry

docker pull <image name>

Push an image or repo to a registry

docker push <repository address> <image name>

Search for an image on docker hub

docker search <image name>

Load image from a tar archive

docker load <image tar file> 

Save one image or more to a tar archive

docker save <file name> <options>

Login with Docker ID at Docker Hub

docker login

 

Build

 

Create an image from a dockerfile 

docker build <options> <path to dockerfile>
  -t <image name>

Run a command in a new container

docker run <options> <image name> <command>

Create a new container

docker create <Image name> <options> <command>

Create images using a git remote repository

docker git <git repository address>

Create a container with a custom name

docker container create -ti --name <container name> <image name>

 

Inspecting / Interacting

 

Show information about a container 

docker inspect <container name>

List the processes inside the container

docker top <container name> <options>

List the logfile of the container

docker logs <container name>

Run a command in an existing container

docker exec <container name> <command>

Export a container to tar archive

docker export <container name>

Attach to a running container

docker attach <container name>

Copy files from the given container

docker cp <container name:path> hostpath\-

Copy files to the given container

docker cp hostpath\-<container name:path>

Get live stream statistics of given container

docker stats <container name>

List the installed plugins of docker

docker plugin ls

 

Clean up

 

Remove unused images

docker image prune

Remove all images 

docker image prune -a 

Prune your entire system

docker system prune

Kill all running containers

docker kill $(docker ps -q)

 

Author: Ralf Menti