create k8s user, certificate, permissions and client config

create-kube-user.sh

#!/bin/bash

CLUSTERNAME=mycluster.mydomain
NAMESPACE=default
USERNAME=myclusteruser
GROUPNAME=mygroup

openssl genrsa -out ${USERNAME}.key 2048

CSR_FILE=$USERNAME.csr
KEY_FILE=$USERNAME.key

openssl req -new -key $KEY_FILE -out $CSR_FILE -subj "/CN=$USERNAME/O=$GROUPNAME"

CERTIFICATE_NAME=$USERNAME.$NAMESPACE

cat <<EOF | kubectl create -f -
apiVersion: certificates.k8s.io/v1beta1
kind: CertificateSigningRequest
metadata:
  name: $CERTIFICATE_NAME 
spec:
  groups:
  - system:authenticated
  request: $(cat $CSR_FILE | base64 | tr -d '\n')
  usages:
  - digital signature
  - key encipherment
  - server auth
EOF

kubectl certificate approve $CERTIFICATE_NAME

CRT_FILE=$USERNAME.crt

kubectl get csr $CERTIFICATE_NAME -o jsonpath='{.status.certificate}'  | base64 -D > $CRT_FILE

cat <<EOF | kubectl create -f -
kind: Role
apiVersion: rbac.authorization.k8s.io/v1beta1
metadata:
  namespace: $NAMESPACE
  name: deployment-manager
rules:
- apiGroups: ["", "extensions", "apps"]
  resources: ["deployments", "replicasets", "pods"]
  verbs: ["get", "list", "watch", "create", "update", "patch", "delete"] # You can also use ["*"]
EOF


cat <<EOF | kubectl create -f -
kind: RoleBinding
apiVersion: rbac.authorization.k8s.io/v1beta1
metadata:
  name: $USERNAME-deployment-manager-binding
  namespace: $NAMESPACE
subjects:
- kind: User
  name: $USERNAME
  apiGroup: ""
roleRef:
  kind: Role
  name: deployment-manager
  apiGroup: ""
EOF

kubectl config set-credentials $USERNAME \
  --client-certificate=$(pwd)/$CRT_FILE \
  --client-key=$(pwd)/$KEY_FILE

kubectl config set-context $USERNAME-context --cluster=$CLUSTERNAME --namespace=$NAMESPACE --user=$USERNAME

Hi guys!
Thanks for your updates and hints on this!
I'm currently not working with any kubernetes installation, so I have no possibilities (and time) to test and comment on these things... actually I dont even remember completely how I wrote it.
Vaguely I remember it's partly command copied from some kubernetes docs(2 years ago!), banged together in one script and made more flexible with the variables so it can be executed simply and repeatedly, without error-prone manual interaction.
It's 2 years old, so i'm, surprised it still works halfway for a fast changing software as k8s. Also, I think I remember being surprised that a thing as "create a user" needed such a lot of additional scripting - and I'm again surprised this is still the case.
But great if this helped you a bit.

Hope sometime I will be able to play with k8s stuff again and try your changes :)