my goal is to execute a script once on a permanently running pod in kubernetes. The pod is called busybox-<SOME_ID> and finds itself in the namespace default.Therefore, I wrote this script - called scan-one-pod.sh:

#!/bin/bash
export MASTER_IP=192.168.56.102
export SCRIPT_NAME=script.sh
export POD_NAMESPACE=default
export POD_NAME=busybox

echo "echo HALLO" | ssh ubuntu@$MASTER_IP
export POD_ID=$(kubectl get po | grep busybox | sed -n '1p'|awk '{print $1}')
kubectl cp $SCRIPT_NAME $POD_NAMESPACE/$POD_ID:.
kubectl exec  $POD_ID -- chmod +x $SCRIPT_NAME
export CONTAINER_ID=$(kubectl describe pod busybox | grep 'Container ID' | sed -n '1p'|awk '{print $3}')
ssh -t ubuntu@$MASTER_IP "sudo docker exec -u root $CONTAINER_ID -- ./script.sh"

The referred script script.sh has the following content:

$ kubectl exec  $POD_ID --  cat script.sh
#!/bin/bash
echo "test" >> test
cp test test-is-working

However, it is not possible to run the script on the pod:

• the files test and test-is-working are not created

• the script scan-one-pod.sh returns just EOF:

  $ ./scan-one-pod.sh
  Pseudo-terminal will not be allocated because stdin is not a terminal.
  Welcome to Ubuntu 16.04.3 LTS (GNU/Linux 4.4.0-87-generic x86_64)
  
   * Documentation:  https://help.ubuntu.com
   * Management:     https://landscape.canonical.com
   * Support:        https://ubuntu.com/advantage
  
  155 Software-Pakete können aktualisiert werden.
  72 Aktualisierungen sind Sicherheitsaktualisierungen.
  
  
  HALLO
  [sudo] Passwort für ubuntu:
  EOF
  Connection to 192.168.56.102 closed.

• If I execute the docker-command directly, remote on my kubernetes-controller, I get the same message of EOF:

  ubuntu@controller:~$ export CONTAINER_ID=$(kubectl describe pod busybox | grep 'Container ID' | sed -n '1p'|awk '{print $3}')
  ubuntu@controller:~$ sudo docker exec -u root $CONTAINER_ID  ./script.sh
  EOF
  

• If I execute it from my local workstation via kubectl exec I get this error:

  $ kubectl exec  $POD_ID  ./script.sh
  rpc error: code = 13 desc = invalid header field value "oci runtime error: exec failed: container_linux.go:247: starting container process caused \"no such file or directory\"\n"

  I don't know, which missing file they are referring to, but the script.sh-file is present and the busybox-pod seems to be running:

  $ kubectl exec  $POD_ID  ls script.sh
  script.sh
  
  $ kubectl get po busybox-6bdf9b5bbc-4skds
  NAME                       READY     STATUS    RESTARTS   AGE
  busybox-6bdf9b5bbc-4skds   1/1       Running   10         12d

Question: As far as I know, EOF means End-Of-File. End of which file would be important for me to know, and why is that a problem?

Thanks in advance, any help is appreciated :)