As a developer sometimes I need to debug or investigate problems on the cloud machine. so I create this cheat sheet to note the commands. And it might be good to share with people who are just getting started with the Kubernetes.
Pod, Namespace, and Deployment
to using kubectl, the reader need to know some knowledge about pod, namespace, and containers in Kubernetes.
Container
Kubernates Container is similar to Docker Container it will include software or package to runnning on it environments or OS. And the pre running container is calling Container Image similar to Docker Image.
Pod
Pod is the smallest computing unit in Kubernetes that will share resource and storage. One pod can have multiple containers.
Namespace
namespace will use to define the unique name of group or cluster for multiple objects. normally they will use namespace to specific team or project for make it easier to manage and avoid the effect between team or project.
Deployment
A resource object in Kubernetes that provides declarative updates to applications. for example image, number of pods, etc. normallt it will write in .yaml format.
Google Kubernetes Engine Cluster
to make the kubectl work, we need to set the config. for manual set can follow this guide https://kubernetes.io/docs/tasks/access-application-cluster/access-cluster/.
I am using Google Kubernetes Engine (GKE) they have the gcloud container command to allow me to manage containers and cluster easier.
to map configuration with gcloud cli
# init gcloud
gcloud init
# login
gcloud auth login
# list gcloud config
gcloud config list
# list project
gcloud projects list
# list clusters by project
gcloud container clusters list --project <project-name>
# map kubectl config, for zone copy from the `Location` when list cluster
gcloud container clusters get-credentials <cluster-name> --zone <zone>
# check kubectl config
kubectl config view
After this your kubectl will using access from the gcloud cluster
Kubectl commands
Config
The cluster is the physical platform where all Kubernetes components, capabilities, and workloads are configured.
The context is a set of access parameters that contains a Kubernetes cluster, a user, and a namespace.
# list contexts
kubectl config get-contexts
# set context
kubectl config set-context <context-name>
# list clusters
kubectl config get-clusters
# set cluster
kubectl config set-cluster <cluster-name>
Kubectl apply
kubectl apply -f ./my-manifest.yaml
kubectl apply -f ./my1.yaml -f ./my2.yaml
kubectl apply -f ./dir
Run a Pod
kubectl run busybox --image=busybox --command --restart=Never -- tail -f /dev/null
Find resource name
Resource name will help to identify the Kubernates resource and target such as Service, Pod, Deployment, etc.
List pods
# list pods by all namespaces
kubectl get pod -A
# list pods by namespace
kubectl get pod -n <name-space>
List deployment
# list deployment by namespace
kubectl get deployment -n <name-space>
List all
# list all by namespace
kubectl get all -n <name-space>
# list service, pod, and deployment by namespace
kubectl get service,pod,deployment -n <name-space>
Describe
kubectl describe nodes <name-node>
kubectl describe pods <name-pod>
Logs
# get pod logs
kubectl logs <pod-name>
# get pod logs stream
kubectl logs -f <pod-name>
# get deployment logs
kubectl logs deploy/<deployment-name>
Get expose port
kubectl get svc -n <name-space>
Environment
# set env
kubectl set env <resource-name> -n <name-space> {ENV_NAME}={ENV_VALUE}
# remove env, to remove env need to add `-` after the env name
kubectl set env <resource-name> -n <name-space> {ENV_NAME}-
# list all pods env
kubectl set env pods --all --list
Forward port
Forward port will allow you access to the Kubernates cluster and mapping with your local port
kubectl port-forward -n <name-space> <resource-name> <local-port>:<resource-port>
# example
kubectl port-forward -n <name-space> <resource-name> 8080:80
Exec
runnning shell on Kubectl pod
if you familiar to Docker it work similar to docker exec
# run shell command
kubectl -n <name-space> exec <pod-name> -- <cmd>
# get env of pod by shell
kubectl -n <name-space> exec <pod-name> -- env
# interactive mode
kubectl -n <name-space> exec -it <pod-name> -- bash