Kubectl — Kubernetes CLI

Kubernetes

Published

December 4, 2024

Modified

May 23, 2025

Installation

Install the kubectl binary to the user home-directory

version=$(curl -L -s https://dl.k8s.io/release/stable.txt)
binary_url=https://dl.k8s.io/release/$version/bin/linux/amd64/kubectl
curl -L $binary_url -o ~/bin/kubectl && chmod +x ~/bin/kubectl

# example for loading tab-completion
source <(kubectl completion bash)

Find a script kubectl-install¹ for Linux on Github

Plugin Manager

Install Krew plugin manager² manual …or use krew-install³

wget https://github.com/kubernetes-sigs/krew/releases/download/v0.4.5/krew-linux_amd64.tar.gz
tar -xvf krew-linux_amd64.tar.gz
cp krew-linux_amd64 ~/bin/krew
krew install krew

# add following to your shell environment
export PATH="${KREW_ROOT:-$HOME/.krew}/bin:$PATH"

Useful plugins⁴…

# required for ctx/ns
sudo dnf install -y fzf
1kubectl krew install ctx
kubectl krew install ns
2kubectl krew install tree
3kubectl krew install stern

1: ctx⁵ for context switching & ns to switch namespaces
2: tree⁶ display resources as tree
3: stern⁷ multi pod and container log tailing

Configuration

Custom configuration file:

export KUBECONFIG=$(realpath kubeconfig.yml)
# check your current context
kubectl config view
# check resource access
kubectl auth can-i get pods

kubeconfig file loading order…

--kubeconfig command option
$KUBECONFIG environment variable
~/.kube/config in the user home-directory

Configuration may include clusters, users & contexts⁸

# list available contexts
kubectl config get-contexts

# set current context in kubeconfig
kubectl config get-contexts $name

Commands

`kubectl run`

# start an interactive container…
kubectl run $pod_name --image=$image --restart=Never --stdin --tty
kubectl delete pods $pod_name

# specific shell
kubectl run $pod_name --image=$image --restart=Never -it --rm -- /bin/bash

# specific application (Perl in this example)
kubectl run $pod_name --image=perl --restart=OnFailure -- perl -Mbignum=bpi -wle 'print bpi(2000)'

kubectl run⁹ common options:

--image= — which container image to use
-it aka --stdin & --tty — spawn an interactive shell
- …allocate a terminal for each container
- …keep stdin open (even if empty)
Clean up…
- --restart=Never — pod should never be restarted
- --rm — automatically remove pod after exit

`kubectl exec`

# execute a command in a specified pod
kubectl exec $pod_name -- curl -s https://10.20.30.40

# specify a container
kubectl exec $pod_name -c $container_name #...

# start an interactive shell
kubectl exec -it my-pod -- /bin/bash

Use cases…

…debugging & diagnostics …for example check logs, inspect files
…modify configuration files & environment variables
…run test scripts …validate application behavior

# copy file to & from containers
kubectl cp /local/path  $pod_name:/path/in/container
kubectl cp $pod_name:/path/in/container /local/path

`kubectl logs`

# show logs entires from the last rotation
kubectl logs $pod_name

# show logs for a specific container
kubectl logs $pod_name -c $container_name

Containerized application log to stdout/stderr…

…automatically rotated daily …every time the logs reaches 10MB
…logs deleted when the pod is deleted

`kubectl apply`

Imperative commands — Fail if a resource exists already

# run an instance of the nginx container by creating a deployment object
kubectl create deployment nginx --image nginx

# create the objects defined in a configuration file
kubectl create -f deployment.yaml

# update the objects defined in a configuration file
# note: dropping all changes to the object missing from the configuration file
kubectl replace -f deployment.yaml

Declarative commands — Create new or modify existing objects

…create, update, and delete operations are automatically detected per-object
…retains changes, even if the changes are not in the object configuration file

# apply changes
kubectl apply -f nginx/
# see what changes are going to be made
kubectl diff -f nginx/
# use option -R for recursive directory decent

Ecosystem

k9s TUI for Kuberntes¹⁰

Configuration…
- k9s info to check config paths
- …for terminal colors with custom skin¹¹
Keyboard short cuts…
- ctrl-q or :q (Vi style) to exit
- ctrl-d delete a resource
- ctrl-k kill a resource (no confirmation!)

Footnotes

kubectl Install Script, GitHub
https://github.com/vpenso/kubernetes-playground/blob/master/bin/kubectl-install ↩︎
Krew Project
https://krew.sigs.k8s.io
https://github.com/kubernetes-sigs/krew ↩︎
krew-install Script, Github
https://github.com/vpenso/kubernetes-playground/blob/master/bin/krew-install ↩︎
List of kubectl plugins, Krew Documentation
https://krew.sigs.k8s.io/plugins ↩︎
kubectx + kubens: Power tools for kubectl, GitHub
https://github.com/ahmetb/kubectx ↩︎
kubectl tree Plugin, GitHub
https://github.com/ahmetb/kubectl-tree ↩︎
Stern kubectl Plugin, Github
https://github.com/stern/stern ↩︎
Configure Access to Multiple Clusters, Kubernetes Documentation
https://kubernetes.io/docs/tasks/access-application-cluster/configure-access-multiple-clusters/↩︎
kubectl run, Documentation
https://kubernetes.io/docs/reference/generated/kubectl/kubectl-commands#run ↩︎
K9s Kubernetes CLI
https://k9scli.io
https://github.com/derailed/k9s
https://k9scli.io/topics/commands ↩︎
K9s Skins, GitHub
https://thelinuxnotes.com/k9s-skins-preview
https://github.com/derailed/k9s/tree/master/skins ↩︎

--- title: 'Kubectl — Kubernetes CLI' categories: - Kubernetes date: 2024/12/04 date-modified: 2025/05/23 toc-expand: true toc-depth: 4 --- ## Installation Install the `kubectl` binary to the user home-directory ```bash version=$(curl -L -s https://dl.k8s.io/release/stable.txt) binary_url=https://dl.k8s.io/release/$version/bin/linux/amd64/kubectl curl -L $binary_url -o ~/bin/kubectl && chmod +x ~/bin/kubectl # example for loading tab-completion source <(kubectl completion bash) ``` Find a script `kubectl-install`[^fgH3J] for Linux on Github [^fgH3J]: `kubectl` Install Script, GitHub <https://github.com/vpenso/kubernetes-playground/blob/master/bin/kubectl-install> ## Plugin Manager Install [Krew]{.mark} plugin manager[^6ghB2] manual …or use `krew-install`[^7gT34] [^6ghB2]: Krew Project <https://krew.sigs.k8s.io> <https://github.com/kubernetes-sigs/krew> [^7gT34]: `krew-install` Script, Github <https://github.com/vpenso/kubernetes-playground/blob/master/bin/krew-install> ```bash wget https://github.com/kubernetes-sigs/krew/releases/download/v0.4.5/krew-linux_amd64.tar.gz tar -xvf krew-linux_amd64.tar.gz cp krew-linux_amd64 ~/bin/krew krew install krew # add following to your shell environment export PATH="${KREW_ROOT:-$HOME/.krew}/bin:$PATH" ``` Useful plugins[^k4DFg]… [^k4DFg]: List of `kubectl` plugins, Krew Documentation <https://krew.sigs.k8s.io/plugins> ```bash # required for ctx/ns sudo dnf install -y fzf kubectl krew install ctx #<1> kubectl krew install ns kubectl krew install tree #<2> kubectl krew install stern #<3> ``` 1. `ctx`[^5Fg3D] for context switching & `ns` to switch namespaces 2. `tree`[^l3SDc] display resources as tree 3. `stern`[^0LdFg] multi pod and container log tailing [^5Fg3D]: `kubectx` + `kubens`: Power tools for kubectl, GitHub <https://github.com/ahmetb/kubectx> [^l3SDc]: `kubectl tree` Plugin, GitHub <https://github.com/ahmetb/kubectl-tree> [^0LdFg]: Stern `kubectl` Plugin, Github <https://github.com/stern/stern> ## Configuration Custom configuration file: ```bash export KUBECONFIG=$(realpath kubeconfig.yml) # check your current context kubectl config view # check resource access kubectl auth can-i get pods ``` kubeconfig file loading order… - `--kubeconfig` command option - `$KUBECONFIG` environment variable - `~/.kube/config` in the user home-directory Configuration may include clusters, users & contexts[^f4GHp] [^f4GHp]: Configure Access to Multiple Clusters, Kubernetes Documentation <https://kubernetes.io/docs/tasks/access-application-cluster/configure-access-multiple-clusters/> ```bash # list available contexts kubectl config get-contexts # set current context in kubeconfig kubectl config get-contexts $name ``` ## Commands ### `kubectl run` ```bash # start an interactive container… kubectl run $pod_name --image=$image --restart=Never --stdin --tty kubectl delete pods $pod_name # specific shell kubectl run $pod_name --image=$image --restart=Never -it --rm -- /bin/bash # specific application (Perl in this example) kubectl run $pod_name --image=perl --restart=OnFailure -- perl -Mbignum=bpi -wle 'print bpi(2000)' ``` `kubectl run`[^ZXQD7] common options: - `--image=` — which container image to use - `-it` aka `--stdin` & `--tty` — spawn an interactive shell - …allocate a terminal for each container - …keep `stdin` open (even if empty) - Clean up… - `--restart=Never` — pod should never be restarted - `--rm` — automatically remove pod after exit [^ZXQD7]: `kubectl run`, Documentation <https://kubernetes.io/docs/reference/generated/kubectl/kubectl-commands#run> ### `kubectl exec` ```bash # execute a command in a specified pod kubectl exec $pod_name -- curl -s https://10.20.30.40 # specify a container kubectl exec $pod_name -c $container_name #... # start an interactive shell kubectl exec -it my-pod -- /bin/bash ``` Use cases… - …debugging & diagnostics …for example check logs, inspect files - …modify configuration files & environment variables - …run test scripts …validate application behavior ```bash # copy file to & from containers kubectl cp /local/path $pod_name:/path/in/container kubectl cp $pod_name:/path/in/container /local/path ``` ### `kubectl logs` ```bash # show logs entires from the last rotation kubectl logs $pod_name # show logs for a specific container kubectl logs $pod_name -c $container_name ``` Containerized application log to stdout/stderr… - …automatically rotated daily …every time the logs reaches 10MB - …logs deleted when the pod is deleted ### `kubectl apply` **Imperative commands** — Fail if a resource exists already ```bash # run an instance of the nginx container by creating a deployment object kubectl create deployment nginx --image nginx # create the objects defined in a configuration file kubectl create -f deployment.yaml # update the objects defined in a configuration file # note: dropping all changes to the object missing from the configuration file kubectl replace -f deployment.yaml ``` **Declarative commands** — Create new or modify existing objects - …create, update, and delete operations are automatically detected per-object - …retains changes, even if the changes are not in the object configuration file ```bash # apply changes kubectl apply -f nginx/ # see what changes are going to be made kubectl diff -f nginx/ # use option -R for recursive directory decent ``` # Ecosystem `k9s` TUI for Kuberntes[^l90dF] * Configuration… - `k9s info` to check config paths - …for terminal colors with custom skin[^l9d35] * Keyboard short cuts… - **ctrl-q** or `:q` (Vi style) to exit - **ctrl-d** delete a resource - **ctrl-k** kill a resource (no confirmation!) [^l90dF]: K9s Kubernetes CLI <https://k9scli.io> <https://github.com/derailed/k9s> <https://k9scli.io/topics/commands> [^l9d35]: K9s Skins, GitHub <https://thelinuxnotes.com/k9s-skins-preview> <https://github.com/derailed/k9s/tree/master/skins> [^p65mV]: Kubetail, GitHub <https://github.com/johanhaleby/kubetail>