Runs commands in K8s pods when those are not installed there but they're in the worker node

run-cmd-pod.sh

#!/bin/bash
#------------------------------------------------------------------------
# run-cmd-pod.sh
#
#  Runs commands in K8s pods when those are not installed there
#  but they're in the worker node.
#
#  Motivation: You want to run a command in a pod without
#  installing anything in the pod. If that command exists
#  in the worker node running the pod, then you can use
#  this script
# 
#  We're assuming here the pod is just running one container
#
#  Example:
#    ./run-cmd-pod.sh pod-6d7d497f4d-6h65k "dig +short www.google.com"
#
#------------------------------------------------------------------------
set -euo pipefail

pod_name=$1
command=$2

container_id=$(kubectl get po ${pod_name} -o jsonpath='{.status.containerStatuses[0].containerID}' | cut -c 10-21)

node=$(kubectl get po ${pod_name} -o jsonpath='{.spec.nodeName}')

pid=$(ssh -o StrictHostKeyChecking=no ${node} "sudo docker inspect --format '{{ .State.Pid }}' ${container_id}")

ssh -o StrictHostKeyChecking=no ${node} "sudo nsenter -t ${pid} -n ${command}"