Create a service account and generate a kubeconfig file for it - this will also set the default namespace for the user

kubernetes_add_service_account_kubeconfig.sh

#!/bin/bash
set -e
set -o pipefail

# Add user to k8s using service account, no RBAC (must create RBAC after this script)
if [[ -z "$1" ]] || [[ -z "$2" ]]; then
 echo "usage: $0 <service_account_name> <namespace>"
 exit 1
fi

SERVICE_ACCOUNT_NAME=$1
NAMESPACE="$2"
KUBECFG_FILE_NAME="/tmp/kube/k8s-${SERVICE_ACCOUNT_NAME}-${NAMESPACE}-conf"
TARGET_FOLDER="/tmp/kube"

create_target_folder() {
    echo -n "Creating target directory to hold files in ${TARGET_FOLDER}..."
    mkdir -p "${TARGET_FOLDER}"
    printf "done"
}

create_service_account() {
    echo -e "\\nCreating a service account in ${NAMESPACE} namespace: ${SERVICE_ACCOUNT_NAME}"
    kubectl create sa "${SERVICE_ACCOUNT_NAME}" --namespace "${NAMESPACE}"
}

get_secret_name_from_service_account() {
    echo -e "\\nGetting secret of service account ${SERVICE_ACCOUNT_NAME} on ${NAMESPACE}"
    SECRET_NAME=$(kubectl get sa "${SERVICE_ACCOUNT_NAME}" --namespace="${NAMESPACE}" -o json | jq -r .secrets[].name)
    echo "Secret name: ${SECRET_NAME}"
}

extract_ca_crt_from_secret() {
    echo -e -n "\\nExtracting ca.crt from secret..."
    kubectl get secret --namespace "${NAMESPACE}" "${SECRET_NAME}" -o json | jq \
    -r '.data["ca.crt"]' | base64 -D > "${TARGET_FOLDER}/ca.crt"
    printf "done"
}

get_user_token_from_secret() {
    echo -e -n "\\nGetting user token from secret..."
    USER_TOKEN=$(kubectl get secret --namespace "${NAMESPACE}" "${SECRET_NAME}" -o json | jq -r '.data["token"]' | base64 -D)
    printf "done"
}

set_kube_config_values() {
    context=$(kubectl config current-context)
    echo -e "\\nSetting current context to: $context"

    CLUSTER_NAME=$(kubectl config get-contexts "$context" | awk '{print $3}' | tail -n 1)
    echo "Cluster name: ${CLUSTER_NAME}"

    ENDPOINT=$(kubectl config view \
    -o jsonpath="{.clusters[?(@.name == \"${CLUSTER_NAME}\")].cluster.server}")
    echo "Endpoint: ${ENDPOINT}"

    # Set up the config
    echo -e "\\nPreparing k8s-${SERVICE_ACCOUNT_NAME}-${NAMESPACE}-conf"
    echo -n "Setting a cluster entry in kubeconfig..."
    kubectl config set-cluster "${CLUSTER_NAME}" \
    --kubeconfig="${KUBECFG_FILE_NAME}" \
    --server="${ENDPOINT}" \
    --certificate-authority="${TARGET_FOLDER}/ca.crt" \
    --embed-certs=true

    echo -n "Setting token credentials entry in kubeconfig..."
    kubectl config set-credentials \
    "${SERVICE_ACCOUNT_NAME}-${NAMESPACE}-${CLUSTER_NAME}" \
    --kubeconfig="${KUBECFG_FILE_NAME}" \
    --token="${USER_TOKEN}"

    echo -n "Setting a context entry in kubeconfig..."
    kubectl config set-context \
    "${SERVICE_ACCOUNT_NAME}-${NAMESPACE}-${CLUSTER_NAME}" \
    --kubeconfig="${KUBECFG_FILE_NAME}" \
    --cluster="${CLUSTER_NAME}" \
    --user="${SERVICE_ACCOUNT_NAME}-${NAMESPACE}-${CLUSTER_NAME}" \
    --namespace="${NAMESPACE}"

    echo -n "Setting the current-context in the kubeconfig file..."
    kubectl config use-context "${SERVICE_ACCOUNT_NAME}-${NAMESPACE}-${CLUSTER_NAME}" \
    --kubeconfig="${KUBECFG_FILE_NAME}"
}

create_target_folder
create_service_account
get_secret_name_from_service_account
extract_ca_crt_from_secret
get_user_token_from_secret
set_kube_config_values

echo -e "\\nAll done! Test with:"
echo "KUBECONFIG=${KUBECFG_FILE_NAME} kubectl get pods"
echo "you should not have any permissions by default - you have just created the authentication part"
echo "You will need to create RBAC permissions"
KUBECONFIG=${KUBECFG_FILE_NAME} kubectl get pods

I'm starting it with kubespray setup on coreos-stable
Getting error:

Getting user token from secret...doneerror: current-context is not set

Because of:

core@k8s-01 ~ $ kubectl config view
apiVersion: v1
clusters: []
contexts: []
current-context: ""
kind: Config
preferences: {}
users: []

Also error in decode option pass to base64

base64: invalid option -- 'D'

It shoud be -d in Ubuntu 16.04 and Coreos

base64 --decode should be OK for Linux and MacOS.

Works properly, except for the typo in base64 command. Just use -d instead of -D.

Works great, can someone explain what kind of RBAC rules are needed, it was just working for me.

Works great, can someone explain what kind of RBAC rules are needed, it was just working for me.

I am new to kubernetes, I think if you are made developer to the namespace, you should able to create kubeconf from SA, RBAC rules for the user I have:
rules:

• apiGroups: ["", "batch", "extensions", "apps"]
  resources: [""]
  verbs: [""]

What RBAC rules are needed? Doesn't feel like this is a complete example gist.

# permissions.yaml
---
kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1beta1
metadata:
  name: deliverybot-clusterrolebinding
subjects:
  - kind: ServiceAccount
    name: deliverybot
    namespace: default
roleRef:
  kind: ClusterRole
  name: cluster-admin
  apiGroup: ""

Heres what I used to get access. You'll want to update the service account name to be whatever you used in ./setup command.

Heres how I did it. First I saved the above in a file names permissions.yaml and ran the following.

chmod +x setup.sh
./setup.sh deliverybot default
kubectl apply -f permissions.yaml 
KUBECONFIG=/tmp/kube/k8s-deliverybot-default-conf kubectl get pods

Thanks! I've added new function for creating RBAC, not sure if "sed" will work on MacOS though.

 apply_rbac() {
    echo -e -n "\\nApplying RBAC permissions..."
    sed -e "s|my_account|${SERVICE_ACCOUNT_NAME}|g" -e "s|my_namespace|${NAMESPACE}|g" \
    permissions-template.yaml > permissions_${SERVICE_ACCOUNT_NAME}.yaml     
    kubectl apply -f permissions_${SERVICE_ACCOUNT_NAME}.yaml
    printf "done"
}
apply_rbac

content of permissions-template.yaml

---
kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1beta1
metadata:
  name: my_account-clusterrolebinding
subjects:
  - kind: ServiceAccount
    name: my_account
    namespace: my_namespace
roleRef:
  kind: ClusterRole
  name: cluster-admin
  apiGroup: ""

Full script with some other adjustemnts https://gist.github.com/xtavras/98c6a2625079a78054a907219c976e2b

One gotcha I've encountered is that the service account's secret is not always available immediately after a successful create sa.

AFAICT, the SA token controller eventually creates it, so some may want to add polling logic (which is seen in the kubernetes test coverage of SA token creation).

I'm not sure if there are bash libs for that, but I've found https://godoc.org/k8s.io/apimachinery/pkg/util/wait useful in case anyone else references the above for creating a larger toolset in Go (e.g. with https://github.com/kubernetes/client-go/).

It is prompt me for Username & Password

brew install jq

and this is how to do it with openshift : https://gist.github.com/abdennour/fee44ca16e054c85d484e4cd9efa9f78

Hi, I create a complete project with a part of this wonderful script https://github.com/heralight/k8s-user-tools , don't hesitate to comment it!

Thank you

It takes too much time, is it expected?

Script almost finishes, but ends with:

Error from server (Forbidden): pods is forbidden: User "system:serviceaccount:default:helm-github-actions" cannot list resource "pods" in API group "" in the namespace "default"

Specifically this command:

KUBECONFIG=${KUBECFG_FILE_NAME} kubectl get pods

# permissions.yaml
---
kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1beta1
metadata:
  name: deliverybot-clusterrolebinding
subjects:
  - kind: ServiceAccount
    name: deliverybot
    namespace: default
roleRef:
  kind: ClusterRole
  name: cluster-admin
  apiGroup: ""

Heres what I used to get access. You'll want to update the service account name to be whatever you used in ./setup command.

Heres how I did it. First I saved the above in a file names permissions.yaml and ran the following.

chmod +x setup.sh
./setup.sh deliverybot default
kubectl apply -f permissions.yaml 
KUBECONFIG=/tmp/kube/k8s-deliverybot-default-conf kubectl get pods

Ah - this fixed it. Thanks!

Does this have an effect on the process?
From https://kubernetes.io/docs/concepts/security/service-accounts/

"""
Service Account Token Secrets In Kubernetes v1.24 and later, the LegacyServiceAccountTokenNoAutoGeneration feature gate prevents Kubernetes from automatically creating these tokens for ServiceAccounts. LegacyServiceAccountTokenNoAutoGeneration is enabled by default; in other words, Kubernetes does not create these tokens.
"""

Here is an updated version which creates the api token manually.
https://gist.github.com/sdarwin/ffc5fed82b6128a7549fd6d5696d98a8