Kubernetes | Cheat Sheet
Readings
Kubectl autocomplete
BASH
source < (kubectl completion bash) # setup autocomplete in bash into the current shell, bash-completion package should be installed first. echo "source <(kubectl completion bash)" >> ~/.bashrc
You can also use a shorthand alias for kubectl that also works with completion:
alias k=kubectl complete -F __start_kubectl k
ZSH
source <(kubectl completion zsh) # setup autocomplete in zsh into the current shell echo "[[ $commands[kubectl] ]] && source <(kubectl completion zsh)" >> ~/.zshrc # add autocomplete permanently to your zsh shell
Kubectl context and configuration
Set which Kubernetes cluster kubectl communicates with and modifies configuration information. See Authenticating Across Clusters with kubeconfig documentation for detailed config file information.
kubectl config view # Show Merged kubeconfig settings.
# use multiple kubeconfig files at the same time and view merged config
KUBECONFIG=~/.kube/config:~/.kube/kubconfig2
kubectl config view
# get the password for the e2e user
kubectl config view -o jsonpath='{.users[?(@.name == "e2e")].user.password}'
kubectl config view -o jsonpath='{.users[].name}' # display the first user
kubectl config view -o jsonpath='{.users[*].name}' # get a list of users
kubectl config get-contexts # display list of contexts
kubectl config current-context # display the current-context
kubectl config use-context my-cluster-name # set the default context to my-cluster-name
# add a new user to your kubeconf that supports basic auth
kubectl config set-credentials kubeuser/foo.kubernetes.com --username=kubeuser --password=kubepassword
# permanently save the namespace for all subsequent kubectl commands in that context.
kubectl config set-context --current --namespace=ggckad-s2
# set a context utilizing a specific username and namespace.
kubectl config set-context gce --user=cluster-admin --namespace=foo
&& kubectl config use-context gce
kubectl config unset users.foo # delete user foo
Kubectl apply
apply manages applications through files defining Kubernetes resources. It creates and updates resources in a cluster through running kubectl apply. This is the recommended way of managing Kubernetes applications on production. See Kubectl Book.
Creating objects
Kubernetes manifests can be defined in YAML or JSON. The file extension .yaml, .yml, and .json can be used.
kubectl apply -f ./my-manifest.yaml # create resource(s)
kubectl apply -f ./my1.yaml -f ./my2.yaml # create from multiple files
kubectl apply -f ./dir # create resource(s) in all manifest files in dir
kubectl apply -f https://git.io/vPieo # create resource(s) from url
kubectl create deployment nginx --image=nginx # start a single instance of nginx
# create a Job which prints "Hello World"
kubectl create job hello --image=busybox -- echo "Hello World"
# create a CronJob that prints "Hello World" every minute
kubectl create cronjob hello --image=busybox --schedule="*/1 * * * *" -- echo "Hello World"
kubectl explain pods # get the documentation for pod manifests
# Create multiple YAML objects from stdin
cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: Pod
metadata:
name: busybox-sleep
spec:
containers:
- name: busybox
image: busybox
args:
- sleep
- "1000000"
---
apiVersion: v1
kind: Pod
metadata:
name: busybox-sleep-less
spec:
containers:
- name: busybox
image: busybox
args:
- sleep
- "1000"
EOF
# Create a secret with several keys
cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: Secret
metadata:
name: mysecret
type: Opaque
data:
password: $(echo -n "s33msi4" | base64 -w0)
username: $(echo -n "jane" | base64 -w0)
EOF
Viewing, finding resources
# Get commands with basic output
kubectl get services # List all services in the namespace
kubectl get pods --all-namespaces # List all pods in all namespaces
kubectl get pods -o wide # List all pods in the current namespace, with more details
kubectl get deployment my-dep # List a particular deployment
kubectl get pods # List all pods in the namespace
kubectl get pod my-pod -o yaml # Get a pod's YAML
# Describe commands with verbose output
kubectl describe nodes my-node
kubectl describe pods my-pod
# List Services Sorted by Name
kubectl get services --sort-by=.metadata.name
# List pods Sorted by Restart Count
kubectl get pods --sort-by='.status.containerStatuses[0].restartCount'
# List PersistentVolumes sorted by capacity
kubectl get pv --sort-by=.spec.capacity.storage
# Get the version label of all pods with label app=cassandra
kubectl get pods --selector=app=cassandra -o
jsonpath='{.items[*].metadata.labels.version}'
# Retrieve the value of a key with dots, e.g. 'ca.crt'
kubectl get configmap myconfig
-o jsonpath='{.data.ca.crt}'
# Get all worker nodes (use a selector to exclude results that have a label
# named 'node-role.kubernetes.io/master')
kubectl get node --selector='!node-role.kubernetes.io/master'
# Get all running pods in the namespace
kubectl get pods --field-selector=status.phase=Running
# Get ExternalIPs of all nodes
kubectl get nodes -o jsonpath='{.items[*].status.addresses[?(@.type=="ExternalIP")].address}'
# List Names of Pods that belong to Particular RC
# "jq" command useful for transformations that are too complex for jsonpath, it can be found at https://stedolan.github.io/jq/
sel=${$(kubectl get rc my-rc --output=json | jq -j '.spec.selector | to_entries | .[] | "(.key)=(.value),"'
echo $(kubectl get pods --selector=$sel --output=jsonpath={.items..metadata.name})
# Show labels for all pods (or any other Kubernetes object that supports labelling)
kubectl get pods --show-labels
# Check which nodes are ready
JSONPATH='{range .items[*]}{@.metadata.name}:{range @.status.conditions[*]}{@.type}={@.status};{end}{end}'
&& kubectl get nodes -o jsonpath="$JSONPATH" | grep "Ready=True"
# List all Secrets currently in use by a pod
kubectl get pods -o json | jq '.items[].spec.containers[].env[]?.valueFrom.secretKeyRef.name' | grep -v null | sort | uniq
# List all containerIDs of initContainer of all pods
# Helpful when cleaning up stopped containers, while avoiding removal of initContainers.
kubectl get pods --all-namespaces -o jsonpath='{range .items[*].status.initContainerStatuses[*]}{.containerID}{"n"}{end}' | cut -d/ -f3
# List Events sorted by timestamp
kubectl get events --sort-by=.metadata.creationTimestamp
# Compares the current state of the cluster against the state that the cluster would be in if the manifest was applied.
kubectl diff -f ./my-manifest.yaml
# Produce a period-delimited tree of all keys returned for nodes
# Helpful when locating a key within a complex nested JSON structure
kubectl get nodes -o json | jq -c 'path(..)|[.[]|tostring]|join(".")'
# Produce a period-delimited tree of all keys returned for pods, etc
kubectl get pods -o json | jq -c 'path(..)|[.[]|tostring]|join(".")'
Updating resources
kubectl set image deployment/frontend www=image:v2 # Rolling update "www" containers of "frontend" deployment, updating the image kubectl rollout history deployment/frontend # Check the history of deployments including the revision kubectl rollout undo deployment/frontend # Rollback to the previous deployment kubectl rollout undo deployment/frontend --to-revision=2 # Rollback to a specific revision kubectl rollout status -w deployment/frontend # Watch rolling update status of "frontend" deployment until completion kubectl rollout restart deployment/frontend # Rolling restart of the "frontend" deployment cat pod.json | kubectl replace -f - # Replace a pod based on the JSON passed into std # Force replace, delete and then re-create the resource. Will cause a service outage. kubectl replace --force -f ./pod.json # Create a service for a replicated nginx, which serves on port 80 and connects to the containers on port 8000 kubectl expose rc nginx --port=80 --target-port=8000 # Update a single-container pod's image version (tag) to v4 kubectl get pod mypod -o yaml | sed 's/(image: myimage):.*$/1:v4/' | kubectl replace -f - kubectl label pods my-pod new-label=awesome # Add a Label kubectl annotate pods my-pod icon-url=http://goo.gl/XXBTWq # Add an annotation kubectl autoscale deployment foo --min=2 --max=10 # Auto scale a deployment "foo"
Patching resources
# Partially update a node
kubectl patch node k8s-node-1 -p '{"spec":{"unschedulable":true}}'
# Update a container's image; spec.containers[*].name is required because it's a merge key
kubectl patch pod valid-pod -p '{"spec":{"containers":[{"name":"kubernetes-serve-hostname","image":"new image"}]}}'
# Update a container's image using a json patch with positional arrays
kubectl patch pod valid-pod --type='json' -p='[{"op": "replace", "path": "/spec/containers/0/image", "value":"new image"}]'
# Disable a deployment livenessProbe using a json patch with positional arrays
kubectl patch deployment valid-deployment --type json -p='[{"op": "remove", "path": "/spec/template/spec/containers/0/livenessProbe"}]'
# Add a new element to a positional array
kubectl patch sa default --type='json' -p='[{"op": "add", "path": "/secrets/1", "value": {"name": "whatever" } }]'
Editing resources
Edit any API resource in your preferred editor.
kubectl edit svc/docker-registry # Edit the service named docker-registry KUBE_EDITOR="nano" kubectl edit svc/docker-registry # Use an alternative editor
Scaling resources
kubectl scale --replicas=3 rs/foo # Scale a replicaset named 'foo' to 3 kubectl scale --replicas=3 -f foo.yaml # Scale a resource specified in "foo.yaml" to 3 kubectl scale --current-replicas=2 --replicas=3 deployment/mysql # If the deployment named mysql's current size is 2, scale mysql to 3 kubectl scale --replicas=5 rc/foo rc/bar rc/baz # Scale multiple replication controllers
Deleting resources
kubectl delete -f ./pod.json # Delete a pod using the type and name specified in pod.json
kubectl delete pod,service baz foo # Delete pods and services with same names "baz" and "foo"
kubectl delete pods,services -l name=myLabel # Delete pods and services with label name=myLabel
kubectl -n my-ns delete pod,svc --all # Delete all pods and services in namespace my-ns,
# Delete all pods matching the awk pattern1 or pattern2
kubectl get pods -n mynamespace --no-headers=true | awk '/pattern1|pattern2/{print $1}' | xargs kubectl delete -n mynamespace pod
Interacting with running Pods
kubectl logs my-pod # dump pod logs (stdout) kubectl logs -l name=myLabel # dump pod logs, with label name=myLabel (stdout) kubectl logs my-pod --previous # dump pod logs (stdout) for a previous instantiation of a container kubectl logs my-pod -c my-container # dump pod container logs (stdout, multi-container case) kubectl logs -l name=myLabel -c my-container # dump pod logs, with label name=myLabel (stdout) kubectl logs my-pod -c my-container --previous # dump pod container logs (stdout, multi-container case) for a previous instantiation of a container kubectl logs -f my-pod # stream pod logs (stdout) kubectl logs -f my-pod -c my-container # stream pod container logs (stdout, multi-container case) kubectl logs -f -l name=myLabel --all-containers # stream all pods logs with label name=myLabel (stdout) kubectl run -i --tty busybox --image=busybox -- sh # Run pod as interactive shell kubectl run nginx --image=nginx -n mynamespace # Run pod nginx in a specific namespace kubectl run nginx --image=nginx # Run pod nginx and write its spec into a file called pod.yaml --dry-run=client -o yaml > pod.yaml kubectl attach my-pod -i # Attach to Running Container kubectl port-forward my-pod 5000:6000 # Listen on port 5000 on the local machine and forward to port 6000 on my-pod kubectl exec my-pod -- ls / # Run command in existing pod (1 container case) kubectl exec --stdin --tty my-pod -- /bin/sh # Interactive shell access to a running pod (1 container case) kubectl exec my-pod -c my-container -- ls / # Run command in existing pod (multi-container case) kubectl top pod POD_NAME --containers # Show metrics for a given pod and its containers
Interacting with Nodes and cluster
kubectl cordon my-node # Mark my-node as unschedulable kubectl drain my-node # Drain my-node in preparation for maintenance kubectl uncordon my-node # Mark my-node as schedulable kubectl top node my-node # Show metrics for a given node kubectl cluster-info # Display addresses of the master and services kubectl cluster-info dump # Dump current cluster state to stdout kubectl cluster-info dump --output-directory=/path/to/cluster-state # Dump current cluster state to /path/to/cluster-state # If a taint with that key and effect already exists, its value is replaced as specified. kubectl taint nodes foo dedicated=special-user:NoSchedule
Resource types
List all supported resource types along with their shortnames, API group, whether they are namespaced, and Kind:
kubectl api-resources
Other operations for exploring API resources:
kubectl api-resources --namespaced=true # All namespaced resources kubectl api-resources --namespaced=false # All non-namespaced resources kubectl api-resources -o name # All resources with simple output (just the resource name) kubectl api-resources -o wide # All resources with expanded (aka "wide") output kubectl api-resources --verbs=list,get # All resources that support the "list" and "get" request verbs kubectl api-resources --api-group=extensions # All resources in the "extensions" API group
Formatting output
To output details to your terminal window in a specific format, add the -o (or --output) flag to a supported kubectl command.
| Output format | Description |
|---|---|
-o=custom-columns=<spec> | Print a table using a comma separated list of custom columns |
-o=custom-columns-file=<filename> | Print a table using the custom columns template in the <filename> file |
-o=json | Output a JSON formatted API object |
-o=jsonpath=<template> | Print the fields defined in a jsonpath expression |
-o=jsonpath-file=<filename> | Print the fields defined by the jsonpath expression in the <filename> file |
-o=name | Print only the resource name and nothing else |
-o=wide | Output in the plain-text format with any additional information, and for pods, the node name is included |
-o=yaml | Output a YAML formatted API object |
Examples using -o=custom-columns:
# All images running in a cluster kubectl get pods -A -o=custom-columns='DATA:spec.containers[*].image' # All images excluding "k8s.gcr.io/coredns:1.6.2" kubectl get pods -A -o=custom-columns='DATA:spec.containers[?(@.image!="k8s.gcr.io/coredns:1.6.2")].image' # All fields under metadata regardless of name kubectl get pods -A -o=custom-columns='DATA:metadata.*'
More examples in the kubectl reference documentation.
Kubectl output verbosity and debugging
Kubectl verbosity is controlled with the -v or --v flags followed by an integer representing the log level. General Kubernetes logging conventions and the associated log levels are described here.
| Verbosity | Description |
|---|---|
--v=0 | Generally useful for this to always be visible to a cluster operator. |
--v=1 | A reasonable default log level if you don’t want verbosity. |
--v=2 | Useful steady state information about the service and important log messages that may correlate to significant changes in the system. This is the recommended default log level for most systems. |
--v=3 | Extended information about changes. |
--v=4 | Debug level verbosity. |
--v=6 | Display requested resources. |
--v=7 | Display HTTP request headers. |
--v=8 | Display HTTP request contents. |
--v=9 | Display HTTP request contents without truncation of contents. |
