kubernets.md

Tabels of Contenets:

• Kubernets Cheats Sheets

• Auto completion of kubernets Commands

• Installation of kubectx and kubens

• kube-ps1: Kubernetes prompt for bash

• Make Easy to execute the Command Inside the Container

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Kubernetes Cheats Sheets

1. Kubernets Cheatsheet
2. Kubernets Commands (Kubectl commands Reference)
3. Kubernets reference resources

Auto completion of kubernets Commands

In Bash, we can do autocompletion of kubectl commands

For faster command Execution s example:

Kubectl exec -it ngin

Hit tab you will automatically promt

Kubectl exec -it nginx-f89759699-8rzf8

we need to add lines in the ~/.bashrc

source <(kubectl completion bash)
echo "source <(kubectl completion bash)"
alias k=kubectl
complete -F __start_kubectl k

After Adding just reload the profile by

source ~/.bashrc

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Kubectx

kubectx is a utility to manage and switch between kubectl contexts.

USAGE:
  kubectx                   : list the contexts
  kubectx <NAME>            : switch to context <NAME>
  kubectx -                 : switch to the previous context
  kubectx -c, --current     : show the current context name
  kubectx <NEW_NAME>=<NAME> : rename context <NAME> to <NEW_NAME>
  kubectx <NEW_NAME>=.      : rename current-context to <NEW_NAME>
  kubectx -d <NAME>         : delete context <NAME> ('.' for current-context)
                              (this command won't delete the user/cluster entry
                              that is used by the context)
  kubectx -u, --unset       : unset the current context

Usage

$ kubectx
oregon
minikube

$ kubectx oregon
Switched to context "oregon".

kubens

kubenx is a utility to manage and switch between kubectl namespaces.

USAGE:
  kubens                    : list the namespaces
  kubens <NAME>             : change the active namespace
  kubens -                  : switch to the previous namespace
  kubens -c, --current      : show the current namespace

usage

$ kubens kube-system
Context "test" set.
Active namespace is "kube-system".

$ kubens -
Context "test" set.
Active namespace is "default".

kubens also supports Tab completion on bash/zsh/fish shells.

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Installation of kubectx and kubens

sudo git clone https://github.com/ahmetb/kubectx /opt/kubectx
sudo cp /opt/kubectx/kubectx /usr/local/bin/kubectx
sudo cp /opt/kubectx/kubens /usr/local/bin/kubens

Reference

• kubectx
• kubens

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kube-ps1: Kubernetes prompt for bash

Its Very difficult to know Which Cluster you are in the Kubernets.

There is a script By which, you can able to promt in Bash in which cluster You are in , and which namespace you are in Namespace.

Bash

Download the script and paste in the location.

curl -o https://github.com/jonmosco/kube-ps1/blob/master/kube-ps1.sh ~/kube-ps1.sh

Copy below Commands in the ~/.bashrc

source ~/kube-ps1.sh>>~/.bashrc
PS1='[\u@\h \W $(kube_ps1)]\$ '>>~/.bashrc

After Adding just reload the profile by

source ~/.bashrc

For Autocompletion of kubens and kubectl

git clone https://github.com/ahmetb/kubectx.git ~/.kubectx
COMPDIR=$(pkg-config --variable=completionsdir bash-completion)
ln -sf ~/.kubectx/completion/kubens.bash $COMPDIR/kubens
ln -sf ~/.kubectx/completion/kubectx.bash $COMPDIR/kubectx
cat << EOF >> ~/.bashrc

#kubectx and kubens
export PATH=~/.kubectx:\$PATH
EOF

Your will be promted with Bash Command promt like below

reference:

• Kubernets ps1

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Make Easy to execute the Command Inside the Container

Some times you may need to execute Command, Inside the container to check services, telnet, nslookup

kubectl run multitool --image=praqma/network-multitool -n default

Add below command in the ~/.bashrc

alias kip="kubectl -n default exec -it multitool --">>~/.bashrc

After Adding just reload the profile by

source ~/.bashrc

Then you can execute following Commands inside the pod. By the Below commands.

kip nslookup kubernetes

Kubernetes namespace is in struck

namespace=<deleting_namespace>
kubectl get namespace ${namespace} -o json \
  | tr -d "\n" | sed "s/\"finalizers\": \[[^]]\+\]/\"finalizers\": []/" \
  | kubectl replace --raw /api/v1/namespaces/stucked-namespace/finalize -f -
kubectl delete namespace ${namespace} --grace-period=15 

or

kubectl get namespace ${namespace} -o json > ${namespace}.json
kubectl replace --raw "/api/v1/namespaces/${namespace}/finalize" -f ./${namespace}.json

K8s ingress not deleting

Get the ing

ingress=$(kubectl get ingress  -o custom-columns=":metadata.name")

kubectl patch ingress ${ingress} -p '{"metadata":{"finalizers":[]}}' --type=merge

Get the pods name running in the Node with the labels

Lable="intent=apps"
# get the pods Running
kubectl get nodes -l $Lable | tail -n +2 |awk '{print $1}' | xargs -I {} kubectl describe node {} | awk '/Non-terminated Pods:/, /Allocated resources:/'
# Get the node Events
kubectl get nodes -l $Lable | tail -n +2 | awk '{print $1}' | xargs -I {} kubectl describe node {} | awk '/Events:/, /Name:/'

Delete the jobs with pod failing

errorMessage=image
kubectl delete jobs $(kubectl get po | grep -i $errorMessage | awk {'print $1'} | rev| cut -d'-' -f2- | rev)

limit is for Enforcing, Reqiests is for Allocating resourcse Cgroups(Allocate the Resources), Namespaces(Segregate the resources)

if CPU more --> throtled wait for some time to process requests if Memory more --> OOM killed pods will restart

Get the total CPU and Memory of pods, Helpfull during the HPA

awk '{sum += $3} END {print sum}' <(kubectl top po | tail -n +2 )'

HPA add limits to this

( total resource / deseried pods ) * ( 100 / Desired HPA metrics )