# Kubernetes Cheat Sheet ## kubectl CLI ### Context | | | |--------------------------------------|-----------------------------| |`kubectl config current-context` |Get the current context | |`kubectl config get-contexts` |List all context | |`kubectl config use-context [contextName]`|Set the current context | |`kubectl config delete-context [contextName]`|Delete a context from the config file| ### Namespace | | | |--------------------------------------|-----------------------------| |`kubectl get namespace` |List all namespaces | |`kubectl get ns` |Shortcut | |`kubectl config set-context --current --namespace=[namespaceName]`|Set the current context to use a namespace| |`kubectl create ns` |Create a namespace | |`kubectl delete ns` |Delete a namespace | |`kubectl get pods --all-namespaces` |List all pods in all namespaces| ### Nodes | | | |--------------------------------------|-----------------------------| |`kubectl get nodes` |Get a list of all the installed nodes| |`kubectl describe node [NAME]` |Get some info about a node | ### Pod | | | |--------------------------------------|-----------------------------| |`kubectl create -f [pod-definition.yml]`|Create a pod | |`kubectl run [podname] --image=busybox -- /bin/sh -c "sleep 3600"`|Run a pod (example)| |`kubectl get pods` |List the running pods | |`kubectl get pods -o wide` |Same but with more info | |`kubectl describe pod [podname]` |Show pod info | |`kubectl get pod [podname] -o yaml > file.yaml`|Extract the pod definition in YAML and save it to a file| |`kubectl exec -it [podname] -- sh` |Interactive mode | |`kubectl exec -it [podname] -c [containername] -- sh`|Exec into a pod| |`kubectl delete -f [pod-definition.yml]`|Delete a pod | |`kubectl delete pod [podname]` |Same using the pod's name | |`kubectl logs [podname] -c [containername]`|Get the logs for a container| ### ReplicaSets | | | |--------------------------------------|-----------------------------| |`kubectl apply -f [definition.yaml]` |Create a ReplicaSet | |`kubectl get rs` |List ReplicaSets | |`kubectl describe rs [rsName]` |Get info | |`kubectl delete -f [definition.yaml]` |Delete a ReplicaSet | |`kubectl delete rs [rsName]` |Same but using the ReplicaSet name| ### Deployments | | | |--------------------------------------|-----------------------------| |`kubectl create deploy [deploymentName] --image=busybox --replicas=3 --port=80`|The imperative way| |`kubectl apply -f [definition.yaml]` |Create a deployment | |`kubectl get deploy` |List deployments | |`kubectl describe deploy [deploymentName]`|Get info | |`kubectl get rs` |List replicasets | |`kubectl delete -f [definition.yaml]` |Delete a deployment | |`kubectl delete deploy [deploymentName]`|Same but using the deployment name| ### DaemonSets | | | |--------------------------------------|-----------------------------| |`kubectl apply -f [definition.yaml]` |Create a DaemonSet | |`kubectl get ds` |List DaemonSets | |`kubectl describe ds [rsName]` |Get info | |`kubectl delete -f [definition.yaml]` |Delete a DaemonSet | |`kubectl delete ds [rsName]` |Same but using the DaemonSet name| ### StatefulSets | | | |--------------------------------------|-----------------------------| |`kubectl apply -f [definition.yaml]` |Create a StatefulSet | |`kubectl get sts` |List StatefulSets | |`kubectl describe sts [rsName]` |Get info | |`kubectl delete -f [definition.yaml]` |Delete a StatefulSet | |`kubectl delete sts [rsName]` |Same but using the StatefulSet name| ### Jobs | | | |--------------------------------------|-----------------------------| |`kubectl create job [jobName] --image=busybox`|The imperative way | |`kubectl apply -f [definition.yaml]` |Create a Job | |`kubectl get job` |List jobs | |`kubectl describe job [jobName]` |Get info | |`kubectl delete -f [definition.yaml]` |Delete a job | |`kubectl delete job [jobName]` |Same but using the Job name | ### CronJobs | | | |--------------------------------------|-----------------------------| |`kubectl create cronjob [jobName] --image=busybox --schedule="*/1 * * * *" -- bin/sh -c "date;"`|The imperative way| |`kubectl apply -f [definition.yaml]` |Create a CronJob | |`kubectl get cj` |List CronJobs | |`kubectl describe cj [jobName]` |Get info | |`kubectl delete -f [definition.yaml]` |Delete a CronJob | |`kubectl delete cj [jobName]` |Same but using the CronJob name| ### Misc. | | | |--------------------------------------|-----------------------------| |`kubectl create -f [YAML file]` |Create an object using YAML | --- ### `kubectx` - Separate program that acts as an alias for `kubectl config use-context` - *Fast way to switch between clusters and namespaces in kubectl* --- ### Declarative vs Imperative #### Declarative Example - YAML File ```yaml apiVersion: v1 kind: Pod metadata: name: myapp-pod labels: app: myapp type: front-end spec: containers: name: nginx-container image: nginx ``` #### Imperative Example - Series of commands ```sh kubectl run mynginx --image=nginx --port=80 kubectl create deploy mynginx --image=nginx --port=80 --replicas=3 kubectl create service nodeport myservice --targetPort=8080 kubectl delete pod nginx ``` ### Pod definition - required properties - Root level required properties - `apiVersion` - Api version of the object - `kind` - type of object - `metadata.name` - unique name for the object - `metadata.namespace` - scoped environment name (will default to current) - `spec` - object specifications or desired state --- ### Namespace Example Namespace definition: ```yaml apiVersion: v1 kind: Namespace metadata: name: prod ``` Pod definition: ```yaml apiVersion: v1 # Object type kind: Pod metadata: name: myapp-pod namespace: prod # Labels are used to identify, describe and group related sets of objects or resources together labels: app: myapp type: front-end spec: containers: - name: nginx-container image: nginx ports: # Listening port - containerPort: 80 name: http protocol: TCP # Environment Variables env: - name: DBCON value: connectionstring # Equiv to Docker ENTRYPOINT command: ["/bin/sh", "-c"] args: ["echo ${DBCON}"] ``` --- ### Other kinds of YAML definitions #### NetworkPolicy Example ```yaml kind: NetworkPolicy apiVersion: networking.k8s.io/v1 metadata: namespace: clientb name: deny-from-other-namespaces spec: podSelector: matchLabels: ingress: - from: - podSelector: {} ``` #### ResourceQuota Example ```yaml apiVersion: v1 kind: ResourceQuota metadata: name: compute-quota namespace: prod spec: hard: pods: "10" limits.cpu: "5" limits.memory: 10Gi ``` #### Pod definition --- ### Pod state | | | |------------------------------|----------------------------------------| |Pending |Accepted but not yet created | |Running |Bound to a node | |Succeeded |Exited with status 0 | |Failed |All containers exit and at least one exited with non-zero status| |Unknown |Communication issues with the pod | |CrashLoopBackOff |Started crashed, started again, and then crashed again| --- ### Init Containers Example pod definition that uses init containers ```yaml apiVersion: v1 kind: Pod metadata: name: myapp-pod labels: app: myapp spec: # App container containers: - name: myapp-container image: busybox # Init containers (these will run before the app container) initContainers: - name: init-myservice image: busybox:1.28 command: ['sh', '-c', "until nslookup mysvc.namespace.svc.cluster.local; do echo waiting for my service; sleep 2; done"] - name: init-mydb image: busybox:1.28 command: ['sh', '-c', "until lookup mydb.namespace.svc.cluster.local; do echo waiting for mydb; sleep 2; done"] ``` --- ### Multi-Containers Pods Example of defining multiple containers in a single pod definition ```yaml apiVersion: v1 kind: Pod metadata: name: two-containers spec: restartPolicy: Always containers: # Container #1 - name: mynginx image: nginx ports: - containerPort: 80 # Container #2 - name: mybox image: busybox ports: - containerPort: 81 command: - sleep - "3600" ``` --- ### ReplicaSets Example ReplicaSet definition ```yaml apiVersion: apps/v1 kind: ReplicaSet metadata: name: rs-example spec: replicas: 3 # desired number of instances selector: matchLabels: app: nginx env: front-end template: metadata: labels: app: nginx type: front-end spec: containers: - name: nginx image: nginx:stable-alpine ports: - containerPort: 80 ``` - Top section is specific to ReplicaSets - Section under `template:` specifies the pods you want to run --- ### Deployments Example Deployment definition ```yaml apiVersion: apps/v1 kind: Deployment metadata: name: deploy-example spec: replicas: 3 # number of pod instances revisionHistoryLimit: 3 # number of previous iterations to keep selector: matchLabels: app: nginx env: prod strategy: # Possible strategies are RollingUpdate and Recreate type: RollingUpdate rollingUpdate: maxSurge: 1 maxUnavailable: 1 template: metadata: labels: app: nginx type: prod spec: containers: - name: nginx image: nginx:stable-alpine ports: - containerPort: 80 ``` - Like with ReplicaSets, the section under `template:` specifies the pods you want to run --- ### DaemonSet Example DaemonSet definition ```yaml apiVersion: apps/v1 kind: DaemonSet metadata: name: daemonset-example labels: app: daemonset-example spec: selector: matchLabels: app: daemonset-example template: metadata: labels: app: daemonset-example spec: tolerations: - key: node-role.kubernetes.io/master effect: NoSchedule containers: - name: busybox image: busybox args: - sleep - "10000" ``` --- ### Job Example Job definition ```yaml apiVersion: batch/v1 kind: Job metadata: name: pi spec: activeDeadlineSeconds 30 # Max seconds to run parallelism: 3 # How many pods should run in parallel completions: 3 # How many successful pod completions are needed to mark a job completed template: spec: containers: - name: pi image: perl command: ["perl", "-Mbignum=bpi", "-wle", "print bpi(2000)"] restartPolicy: Never # Default is Always ``` --- ### CronJob Example CronJob definition ```yaml apiVersion: batch/v1beta1 kind: CronJob metadata: name: hello-cron spec: schedule: "* * * * *" # Cron format string jobTemplate: spec: template: spec: containers: - name: busybox image: busybox command: ["echo", "Hello from the CronJob"] restartPolicy: Never ```