Kubernetes (snips)

References

• Kubernetes API
• Kubectl Commands
• Kubectl Cheatsheet

API Objects

Many Kubernetes API objects have shortcuts and can be used without the plural 's'.

OBJECT=cm, configmap
OBJECT=cronjob
OBJECT=daemonset
OBJECT=deployment
OBJECT=endpoint
OBJECT=event
OBJECT=ing, ingress
OBJECT=namespace
OBJECT=node
OBJECT=pv, persistentvolume
OBJECT=pvc, persistentvolumeclaim
OBJECT=pod
OBJECT=pdb, poddisruptionbudget
OBJECT=rs, replicaset
OBJECT=sa, serviceaccount
OBJECT=secretproviderclass
OBJECT=secret
OBJECT=svc, service
OBJECT=statefulset
OBJECT=sc, storageclass

Often used flags

-c, --container
-n, --namespace,
-A, --all-namespaces
-l (show label, requires a resource)
--show-labels (show labels for all resource)
-o, --output (there are many output shapes => wide, json, jsonpath, yaml, go-template, etc.)
-w, --watch
-it, --stdin --tty

See the watch command on MacOS for a broader watch utility , e.g. watch 'kubectl get all

Kubectl Aliases

Shorten kubectl commands by creating a file with a starter set of aliases that leverage bash-completion.

On a Mac, install bash-completion with brew install bash-completion, depending on your version of bash.

• Kubectl aliases
• Kubectl bash completion

Kubectl Command Examples (long form)

OBJECT, RESOURCE, CONTAINER, CONDITION, FILENAME, and STRING variables can be combined to compose different strings depending on what specificity the context needs in the commands below.

• OBJECT - the type of resource to get
• RESOURCE - the name of the resource to get
• CONTAINER - name of container inside of pod
• CONDITION - evicted, error, or crash
• FILENAME - name of file
• STRING - search string

get

Display one or many resources.
kubectl get $OBJECT
kubectl get $OBJECT -w
kubectl get $OBJECT -o wide
kubectl get $OBJECT -o json

Get all resources.
kubectl get all
kubectl get cm,daemonset,deployment,job,ing,pvc,pdb,pod,rs,secret,statefulset,svc

NAMESPACE=the-wheel
kubectl api-resources --verbs=list --namespaced -o name | xargs -n1 kubectl get --show-kind --ignore-not-found "$@" -n $NAMESPACE
kubectl api-resources --verbs=list --namespaced -o name | xargs -n1 kubectl get --show-kind --ignore-not-found -nl -n $NAMESPACE | grep $APPNAME

Get all resources - by filter.
kubectl get configmap,daemonset,deployment,job,ing,pvc,pdb,pod,replicaset,secret,statefulset,svc | grep solr

Get a resource.
RESOURCE=my-pod-67cd4dd5f-j9s24
OBJECT=pod
kubectl get $OBJECT $RESOURCE
+ kubectl get pod my-pod-67cd4dd5f-j9s24

RESOURCE=my-pod-secret
OBJECT=secret
kubectl get $OBJECT $RESOURCE
+ kubectl get secret my-pod-secret

$OBJECT $RESOURCE can also be expressed as $OBJECT/$RESOURCE, e.g. kubectl get pod foo => kubectl get pod/foo

Get a resource - filter by regex.
RESOURCE=my-pod
OBJECT=secret
kubectl get $OBJECT $(kubectl get $OBJECT | grep $RESOURCE | awk '{print $1}')
+ kubectl get secret my-pod-secret

Get a resource - filter by label selector.
kubectl get $OBJECT --show-labels
kubectl get $OBJECT --show-labels | grep $RESOURCE
kubectl get pod -l app=$RESOURCE
kubectl get pod -l app=$RESOURCE --no-headers -o name
kubectl get pod -l app=$RESOURCE --no-headers -o name | awk -F '/' '{print $2}'

Get events - sort by time desc.
kubectl get events --sort-by=.metadata.creationTimestamp

Get secrets - base64 decoded.
kubectl get secret $RESOURCE -o json | jq '.data | map_values(@base64d)'

Get secrets - base64 decoded as file.
kubectl get secret $RESOURCE -o json | '.data | map_values(@base64d)' > ~/filename.json

Get secrets - base64 encoded.
kubectl get secret $APPNAME-$RESOURCE-$OBJECT -o go-template='{{.data.bootstrapPassword|base64decode}}{{"\n"}}'

Get value from resource manifest by following json path.
kubectl get $OBJECT $APPNAME-$RESOURCE-$OBJECT -o jsonpath={.spec.template.spec.containers[0].name}

Get all containers inside a Pod.
kubectl get pod <podname> -o jsonpath='{.spec.containers[*].name}*' $RESOURCE $CONTAINER

delete

Delete resources by filenames, stdin, resources and names, or by resources and label selector.
kubectl delete $OBJECT $RESOURCE
kubectl delete $OBJECT $(kubectl get $OBJECT | grep $STRING | awk '{print $1}')

Forcefully kill a pod named (be careful with this!).
kubectl delete pod $RESOURCE --force --grace-period 0

Delete all evicted, erroring, or crashed pods.
kubectl get pod -n default | grep prod | grep $CONDITION | awk '{print $1}' | xargs kubectl delete pod -n default

describe

Show details of a specific resource or group of resources.
kubectl describe $OBJECT $APPNAME-$RESOURCE-$OBJECT
kubectl describe $OBJECT $(kubectl get $OBJECT | grep $STRING | awk '{print $1}')

cp

Copy files and directories to and from containers.

PODNAME=(e.g. thewheel-app-configurator-67cd4dd5f-j9s24)
DESTINATION_PATH=(e.g. /var/www/wp-content-mount)
SOURCE_PATH=(e.g. ./data/wp-content/plugins)
kubectl cp $SOURCE_PATH $PODNAME:$DESTINATION_PATH

exec

Open console shell in single container pod.
kubectl exec -it $RESOURCE -- /bin/sh

Containers can have a variety of shells, e.g. bash, sh, bin/bash, bin/sh, dash

Open console shell in one of multiple containers in pod.
kubectl exec -it $RESOURCE -c $CONTAINER -- /bin/bash
kubectl exec -it $(kubectl get $OBJECT | grep $STRING | awk '{print $1}') -- /bin/sh

Run commands directly in a container.
kubectl exec -it $RESOURCE -- mysql -uwordpress -phard2find --database=blog < ./data/blog.sql
kubectl exec -it $RESOURCE -- chown -R 33:33 /var/www/wp-content-mount

logs

Print the logs for a container in a pod.
kubectl logs $RESOURCE

Follow log.
kubectl logs -f $RESOURCE
kubectl logs -f $(kubectl get pod | grep $STRING | awk '{print $1}')

Follow log in a specific container.
kubectl logs -f -l "$STRING" -c $RESOURCE

Find specific text or results in log.
kubectl logs -f $(kubectl get pod | grep $STRING | awk '{print $1}') | grep -i 'we are authenticated'
kubectl logs -f $(kubectl get pods | grep transformer | awk '{print $1}') | grep 'ingester = ' | awk '{print $4 $5 $6}' | sort -u

port-forward

Forward one or more local ports to a pod port.
kubectl port-forward $RESOURCE 8080:80
kubectl port-forward pod/$RESOURCE 8080:80
kubectl port-forward pod/$(kubectl get pods | grep $STRING| awk '{print $1}') 8080:80
kubectl port-forward service/$RESOURCE 8080:80

Preserve existing environment variables.
sudo -E kubectl port-forward service/$RESOURCE 8080:80

Port-forward local port to server.
ssh -L 6443:localhost:6443 fusiondev1

Manage cronjobs/jobs

Create job from cronjob
kubectl create job --from=cronjob/$RESOURCE manual-$RESOURCE-job
kubectl delete job $(kubectl get job | grep manual | awk '{print $1}') && kubectl create job --from=cronjob/$RESOURCE manual-$RESOURCE-job

Show status of all jobs
kubectl get job -o json | jq -r '.items[] | .metadata.name + ":" + (.status.conditions[] | select(.status == "True") .type + ":" + .status)' | grep $STRING

CRUD type operations

apply

Apply a configuration to a resource by filename or stdin - performs a diff and only applies changes if the resource already exists.
kubectl apply -f $FILENAME

create

Create a resource from a file or from stdin.
kubectl create -f $FILENAME

patch

Update field(s) of a resource using strategic merge patch.
kubectl patch $OBJECT $RESOURCE

replace

Replace a resource by filename or stdin.

rollout

Manage the rollout of a resource.
kubectl rollout restart $OBJECT $RESOURCE

Cluster/node maintenance

NODE=server-name

Show what pods are on what nodes?
for pod in $(kubectl get pods | grep thewheel | awk '{print $1}'); do echo $pod; kubectl describe pod $pod | grep 'Node:'; done

for pod in $(kubectl get pods -l app=$RESOURCE --no-headers -o name | awk -F '/' '{print $2}'); do echo -n "Checking $pod .... "; kubectl exec "$pod" -- bash -c "ps aux | grep -v grep | grep enable-ssl-passthrough=true" > /dev/null 2>&1 && echo "Good" || echo "Bad"; done

config

kubectl config use-context k3d-k3s-default
kubectl config set-context --current --namespace=team-a

cluster info

kubectl cluster-info

top

Get node resource consumption.
kubectl top node

cordon

Mark node as unschedulable.
kubectl cordon ...

drain

Drain node in preparation for maintenance.
kubectl drain $NODE

uncordon

Mark node as schedulable.
kubectl uncordon ...

proxy

Proxy to a node.
See kubectl proxy

Cluster/node info

api-resources

Print the supported API resources on the server.

api-versions

Print the supported API versions on the server, in the form of "group/version".

completion

Output shell completion code for the specified shell (bash or zsh).

diff

Diff live version against would-be applied version.

explain

Documentation of resources.

top

Display Resource (CPU/Memory/Storage) usage.

version

Print the client and server version information.