Cheat sheets on Eriks training corner

Docker cheat sheet

Mon, 01 Jan 0001 00:00:00 +0000

Docker cheat sheet

On support01 run Docker with sudo (drop it if your user is in the docker group).

Containers

Task	Command
Run in background, publish a port	`sudo docker run -d --name web -p 8080:80 nginx:1.27`
Run interactively, remove on exit	`sudo docker run -it --rm busybox sh`
List running / all	`sudo docker ps` / `sudo docker ps -a`
Logs, follow	`sudo docker logs -f web`
Shell into a running container	`sudo docker exec -it web sh`
Stop / start / restart	`sudo docker stop web` / `start web` / `restart web`
Remove (force)	`sudo docker rm -f web`
Processes, live stats	`sudo docker top web` / `sudo docker stats`
Full detail as JSON	`sudo docker inspect web`
One field from inspect	`sudo docker inspect -f '{{.NetworkSettings.IPAddress}}' web`
Limit resources	`sudo docker run -d --memory 128m --cpus 0.5 nginx:1.27`

Images

Task	Command
Search / pull	`sudo docker search nginx` / `sudo docker pull nginx:1.27`
List / remove	`sudo docker images` / `sudo docker rmi nginx:1.27`
Layer history	`sudo docker history nginx:1.27`
Build from a Dockerfile	`sudo docker build -t myapp:1.0 .`
Tag / push	`sudo docker tag myapp:1.0 registry/myapp:1.0` / `push`
Save / load a tar	`sudo docker save -o myapp.tar myapp:1.0` / `load -i myapp.tar`

Networking

Task	Command
List networks	`sudo docker network ls`
Create a user network	`sudo docker network create appnet`
Attach at run time	`sudo docker run -d --network appnet --name db mysql:8`
Attach / detach later	`sudo docker network connect appnet web` / `disconnect`
Host / no network	`--network host` / `--network none`

Containers on the same user-defined network resolve each other by container name. On the default bridge they do not.

kubectl cheat sheet

Mon, 01 Jan 0001 00:00:00 +0000

kubectl cheat sheet

Run from support01 with ~/.kube/config in place (Lab 01). No sudo.

Setup that saves hours

alias k=kubectl
source <(kubectl completion bash)
complete -o default -F __start_kubectl k
export do="--dry-run=client -o yaml" # then: kubectl run x --image=nginx $do
kubectl config set-context --current --namespace=dev

Ask the cluster instead of the internet

Question	Command
Which kinds exist? short names? namespaced?	`kubectl api-resources`
Which kinds are cluster-scoped?	`kubectl api-resources --namespaced=false`
Which fields does this kind have?	`kubectl explain ingress.spec.rules`
All fields at once	`kubectl explain deploy.spec --recursive`
What can this command do?	`kubectl create --help` (examples at the bottom)
Global flags	`kubectl options`
Client / server version	`kubectl version`
Can I do this?	`kubectl auth can-i create deployments -n dev`

Look around

Task	Command
Cluster reachable?	`kubectl cluster-info`
Nodes with IPs and versions	`kubectl get nodes -o wide`
Everything in a namespace	`kubectl get all -n dev`
All namespaces	`kubectl get pods -A`
Watch changes live	`kubectl get pods -w`
Sorted events	`kubectl get events --sort-by=.lastTimestamp`
Warnings only, everywhere	`kubectl get events -A --field-selector type=Warning`
Resource usage	`kubectl top nodes` / `kubectl top pods`
By label	`kubectl get pods -l app=web`
Custom columns	`kubectl get pods -o custom-columns=NAME:.metadata.name,NODE:.spec.nodeName`

Create and change

Task	Command
Apply a manifest (or a dir)	`kubectl apply -f pod.yaml` / `-f ./manifests/`
Generate YAML without creating	`kubectl run web --image nginx --dry-run=client -o yaml > web.yaml`
Deployment YAML	`kubectl create deploy web --image nginx --dry-run=client -o yaml`
Service for a deployment	`kubectl expose deploy web --port 80 --type NodePort`
Ingress (legacy)	`kubectl create ingress web --rule="web.k8s.lab/*=web-svc:80"`
Edit a live object	`kubectl edit deploy web`
Patch a field	`kubectl patch svc web -p '{"spec":{"type":"NodePort"}}'`
Scale	`kubectl scale deploy web --replicas=3`
Change an image	`kubectl set image deploy/web nginx=nginx:1.28`
Env from a ConfigMap	`kubectl set env deploy/web --from=configmap/app-cfg`
Label / annotate	`kubectl label pod web tier=frontend`
Delete	`kubectl delete -f web.yaml` / `kubectl delete pod web`

Inspect and debug

Task	Command
Everything about an object + events	`kubectl describe pod web`
Live object as YAML	`kubectl get pod web -o yaml`
One field	`kubectl get pod web -o jsonpath='{.status.podIP}'`
Logs, follow, previous crash	`kubectl logs -f web` / `kubectl logs web --previous`
Logs of one container	`kubectl logs web -c sidecar`
Logs by label / via controller	`kubectl logs -l app=web --tail=50` / `kubectl logs deploy/web`
Shell inside	`kubectl exec -it web -- sh`
Throwaway debug Pod	`kubectl run tmp --image busybox --restart=Never -it --rm -- sh`
Port-forward	`kubectl port-forward svc/web 8080:80`
Copy files	`kubectl cp web:/etc/nginx/nginx.conf ./nginx.conf`
Service endpoints	`kubectl get endpointslices -l kubernetes.io/service-name=web`

Workloads

kubectl rollout status deploy/web
kubectl rollout history deploy/web
kubectl rollout undo deploy/web
kubectl rollout restart deploy/web
kubectl get rs -l app=web # which ReplicaSet is active
kubectl get ds -A # DaemonSets
kubectl get sts # StatefulSets

Storage

kubectl get pv # cluster-scoped
kubectl get pvc -A
kubectl describe pvc data # why is it Pending?
kubectl get sc # StorageClasses
kubectl get csidrivers # installed CSI drivers
kubectl get pv -o custom-columns=NAME:.metadata.name,STATUS:.status.phase,CLAIM:.spec.claimRef.name,POLICY:.spec.persistentVolumeReclaimPolicy
kubectl patch pv <pv> -p '{"spec":{"claimRef":null}}' # reuse a Released PV

Gateway API

kubectl get gatewayclass
kubectl get gateway,httproute -A
kubectl describe gateway web-gw # PROGRAMMED + conditions
kubectl describe httproute shop # Accepted + ResolvedRefs
kubectl explain httproute.spec.rules.backendRefs

The CRDs must be installed first - Gateway API is not part of Kubernetes.

Helm cheat sheet

Mon, 01 Jan 0001 00:00:00 +0000

Helm cheat sheet

Helm 3 uses your ~/.kube/config, so it targets the same cluster kubectl does.

Repositories

Task	Command
Add	`helm repo add podinfo https://stefanprodan.github.io/podinfo`
List / update / remove	`helm repo list` / `helm repo update` / `helm repo remove podinfo`
Search a repo	`helm search repo podinfo`
Search Artifact Hub	`helm search hub postgres`
Show all versions	`helm search repo podinfo --versions`

Look before you install

Task	Command
Chart metadata	`helm show chart podinfo/podinfo`
Configurable values	`helm show values podinfo/podinfo`
Readme	`helm show readme podinfo/podinfo`
Render locally, no cluster	`helm template ./myapp`
Render server-side, no install	`helm install web ./myapp --dry-run --debug`

Releases

Task	Command
Install	`helm install web podinfo/podinfo`
Generated name	`helm install podinfo/podinfo --generate-name`
Into a namespace, creating it	`helm install web podinfo/podinfo -n dev --create-namespace`
Override on the command line	`helm install web podinfo/podinfo --set replicaCount=3`
Override from a file	`helm install web podinfo/podinfo -f my-values.yaml`
Wait for readiness	`helm install web podinfo/podinfo --wait --timeout 5m`
List	`helm list` / `helm list -A`
What is deployed	`helm get manifest web` / `helm get values web`
Upgrade	`helm upgrade web podinfo/podinfo --set replicaCount=5`
Upgrade or install	`helm upgrade --install web podinfo/podinfo`
History	`helm history web`
Roll back	`helm rollback web 1`
Uninstall	`helm uninstall web`
Status	`helm status web`

--set beats -f, and a later -f beats an earlier one.