kubectl fluency

alias k=kubectl
export do="--dry-run=client -o yaml"
export now="--force --grace-period=0"
source <(kubectl completion bash)
complete -o default -F __start_kubectl k

# Then the two commands you will use most:
k create deploy web --image=nginx:1.27 --replicas=2 $do > web.yaml
k delete pod stuck $now

# A Pod
k run web --image=nginx:1.27 --port=80 --labels=app=web
k run once --image=busybox:1.36 --restart=Never -- sh -c 'date'
k run web2 --image=nginx:1.27 --command -- sh -c 'sleep 3600'
k run tmp --image=busybox:1.36 -it --rm --restart=Never -- sh

# A Deployment
k create deploy web --image=nginx:1.27 --replicas=3 --port=80

# A Service for an existing object (--type can also be NodePort or LoadBalancer)
k expose deploy web --name=web-svc --port=80 --target-port=8080 --type=ClusterIP

# A Service on its own (the selector becomes app=web, from the name)
k create svc clusterip web --tcp=80:8080

# A ConfigMap
k create cm app-cfg --from-literal=KEY=value --from-file=app.properties
k create cm app-env --from-env-file=.env

# A Secret
k create secret generic db --from-literal=password=s3cret

# A Namespace
k create ns team-a

# Scale, or change the image
k scale deploy web --replicas=5
k set image deploy/web nginx=nginx:1.26

# Labels (a trailing - removes one)
k label pod web tier=frontend --overwrite
k label pod web tier-

# 1. Generate a manifest without touching the cluster
k -n team-a create deploy api --image=nginx:1.27 --replicas=3 $do > api.yaml

# 2. Find the field you need to add, with the exact spelling and type
k explain deploy.spec.strategy
k explain pod.spec.containers.livenessProbe --recursive | less
k explain pod.spec.tolerations

# 3. Edit the file in vim, then apply it
k apply -f api.yaml

# Multi-resource trick: generate a pod, pipe straight into a label change, apply in one line
k run tmp --image=busybox:1.36 --restart=Never $do -- sleep 3600 | k label --local -f - tier=debug -o yaml | k apply -f -

# --help is faster than the docs for flags
k create deploy --help | less
k run --help | grep -A2 -- --command

k get pods -o wide                      # node, IP, nominated node, readiness gates
k get deploy web -o yaml                # the whole object; pipe to grep or less
k get pod web -o json | less
k get pods -o name                      # pod/web, pod/api... handy for xargs and loops
k get pods -A                           # every namespace
k get pods -l app=web,tier!=cache       # label selectors; also 'env in (prod,staging)'
k get pods --show-labels
k get pods --field-selector=status.phase!=Running -A
k get pods --sort-by=.metadata.creationTimestamp
k get events --sort-by=.lastTimestamp -n team-a
k get pods -o custom-columns=NAME:.metadata.name,NODE:.spec.nodeName,IP:.status.podIP
k get pods -w                           # watch; Ctrl+C to stop
k api-resources | grep -i policy        # short names, api groups, namespaced or not
k api-versions | grep autoscaling

# One field
k get deploy web -o jsonpath='{.spec.replicas}'

# A list, space separated
k get pods -o jsonpath='{.items[*].metadata.name}'

# One item per line, several fields: range ... end
k get nodes -o jsonpath='{range .items[*]}{.metadata.name}{" "}{.status.nodeInfo.kubeletVersion}{"\n"}{end}'

# Filter inside a list: the address whose type is InternalIP
k get nodes -o jsonpath='{range .items[*]}{.metadata.name}{" "}{.status.addresses[?(@.type=="InternalIP")].address}{"\n"}{end}'

# Filter whole items: pods on one node
k get pods -A -o jsonpath='{range .items[?(@.spec.nodeName=="cka-worker")]}{.metadata.namespace}{"/"}{.metadata.name}{"\n"}{end}'

# Container images in a Deployment, taints on nodes, the InternalIP of one node
k get deploy web -o jsonpath='{.spec.template.spec.containers[*].image}'
k get nodes -o jsonpath='{range .items[*]}{.metadata.name}{": "}{.spec.taints[*].key}{"\n"}{end}'
k get node cka-worker -o jsonpath='{.status.addresses[?(@.type=="InternalIP")].address}'

# Tabular output sorted by a jsonpath (sorted on the server response, works with custom-columns)
k -n kube-system get pods --sort-by=.metadata.name -o custom-columns=POD:.metadata.name,NODE:.spec.nodeName

# When jsonpath gets ugly, yq is on the exam hosts
k get deploy web -o yaml | yq '.spec.template.spec.containers[].image'

k config get-contexts                            # the * marks the current one
k config use-context kind-cka
k config current-context
k config set-context --current --namespace=team-a  # every later command defaults to team-a
k config view --minify                             # the active cluster, user and namespace only
k config view --minify -o jsonpath='{..namespace}'

# When a kubeconfig is given as a file in the task
k --kubeconfig=/root/other.kubeconfig get nodes
export KUBECONFIG=/root/other.kubeconfig