Service Accounts

Module

A service account provides an identity for processes that run in a Pod.

Overview

At the end of this module, you will :
  • Learn to create a service accounts
  • Learn how to manage access
  • Learn how to secure a Pods

Prerequisites

Create the directory data/sa in your home folder to manage the YAML file needed in this module.
mkdir ~/data/serviceaccount

Create

Kubernetes service accounts provide access control to the Kubernetes API for services running in pods.
Kubernetes enables access control for workloads by providing service accounts. A service account represents an identity for processes that run in a pod. When a process is authenticated through a service account, it can contact the API server and access cluster resources. If a pod doesn’t have an assigned service account, it gets the default service account.
The create command can create a Ingress object based on a yaml file definition.

Exercise n°1

Create a service account call myfirstserviceaccount.
kubectl create serviceaccount myfirstserviceaccount

Exercise n°2

Create a service account named mysecondserviceaccount with a yaml file definition.
~/data/serviceaccount/01_sa.yaml
apiVersion: v1
kind: ServiceAccount
metadata:
name: mysecondserviceaccount
Create a resource based on the previous yaml file definition.
kubectl create -f ~/data/serviceaccount/01_sa.yaml

Get

The get command list the object asked. It could be a single object or a list of multiple objects comma separated. This command is useful to get the status of each object. The output can be formatted to only display some information based on some json search or external tools like tr, sort, uniq.
The default output display some useful information about each services :
  • Name : the name of the newly created resource
  • Secrets : the number of secrets associated
  • Age : the age since his creation

Exercise n°1

List the current service account resources created.
Command
CLI Return
kubectl get serviceaccounts
NAME SECRETS AGE
default 1 1h
myfirstserviceaccount 1 33m

Describe

Once an object is running, it is inevitably a need to debug problems or check the configuration deployed.
The describe command display a lot of configuration information about the Service Accounts (labels, annotations, etc.).
This command is really useful to introspect and debug an object deployed in a cluster.

Exercise n°1

Describe the service account myfirstserviceaccount previously created.
Command
CLI Return
kubectl describe serviceaccount myfirstserviceaccount
Name: myfirstserviceaccount
Namespace: default
Labels: <none>
Annotations: <none>
Image pull secrets: <none>
Mountable secrets: myfirstserviceaccount-token-59xwk
Tokens: myfirstserviceaccount-token-59xwk
Events: <none>

Explain

Kubernetes come with a lot of documentation about his objects and the available options in each one. Those information can be fin easily in command line or in the official Kubernetes documentation.
The explain command allows to directly ask the API resource via the command line tools to display information about each Kubernetes objects and their architecture.

Exercise n°1

Get the documentation of a specific field of a service account resource.
Command
CLI Return
kubectl explain serviceaccount
KIND: ServiceAccount
VERSION: v1
DESCRIPTION:
ServiceAccount binds together: * a name, understood by users, and perhaps
by peripheral systems, for an identity * a principal that can be
authenticated and authorized * a set of secrets
FIELDS:
apiVersion <string>
APIVersion defines the versioned schema of this representation of an
object. Servers should convert recognized schemas to the latest internal
value, and may reject unrecognized values. More info:
https://git.k8s.io/community/contributors/devel/api-conventions.md#resources
automountServiceAccountToken <boolean>
AutomountServiceAccountToken indicates whether pods running as this service
account should have an API token automatically mounted. Can be overridden
at the pod level.
imagePullSecrets <[]Object>
ImagePullSecrets is a list of references to secrets in the same namespace
to use for pulling any images in pods that reference this ServiceAccount.
ImagePullSecrets are distinct from Secrets because Secrets can be mounted
in the pod, but ImagePullSecrets are only accessed by the kubelet. More
info:
https://kubernetes.io/docs/concepts/containers/images/#specifying-imagepullsecrets-on-a-pod
kind <string>
Kind is a string value representing the REST resource this object
represents. Servers may infer this from the endpoint the client submits
requests to. Cannot be updated. In CamelCase. More info:
https://git.k8s.io/community/contributors/devel/api-conventions.md#types-kinds
metadata <Object>
Standard object's metadata. More info:
https://git.k8s.io/community/contributors/devel/api-conventions.md#metadata
secrets <[]Object>
Secrets is the list of secrets allowed to be used by pods running using
this ServiceAccount. More info:
https://kubernetes.io/docs/concepts/configuration/secret

Delete

The delete command delete resources by filenames, stdin, resources and names, or by resources and label selector.
A service account can be deleted only if it is not used by a running Kubernetes resource.
Note that the delete command does NOT do resource version checks, so if someone submits an update to a resource right when you submit a delete, their update will be lost along with the rest of the resource.

Exercise n°1

Delete the previous service account created in command line.
kubectl delete serviceaccount myfirstserviceaccount

Module exercise

The purpose of this section is to manage each steps of the lifecycle of an application to better understand each concepts of the Kubernetes course.
The main objective in this module is to understand how to secure the internal access to respect the least privileges principles.
For more information about the application used all along the course, please refer to the Exercise App > Voting App link in the left panel.
Based on the principles explain in this module, try by your own to handle this steps. The development of a yaml file is recommended.
The file developed has to be stored in this directory : ~/data/votingapp/14_serviceaccounts
Exercise
Solution
  1. 1.
    Create a service account called vote
  2. 2.
    Create a service account called result
  3. 3.
    Configure the vote Pods to use the vote service accounts created
  4. 4.
    Configure the vote Result to use the result service accounts created
Create the service accounts vote and result in command line.
# Create the vote service account
kubectl create serviceaccount vote
# Create the result service account
kubectl create serviceaccount result
Configure the vote Pods to use the vote service account.
~/data/votingapp/14_serviceaccounts/vote.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
name: vote
namespace: voting-app
spec:
replicas: 1
selector:
matchLabels:
name: vote
strategy:
rollingUpdate:
maxSurge: 1
maxUnavailable: 1
type: RollingUpdate
template:
metadata:
labels:
name: vote
spec:
serviceAccountName: vote
automountServiceAccountToken: false
containers:
- env:
- name: "OPTION_A"
valueFrom:
configMapKeyRef:
name: vote
key: option_a
- name: "OPTION_B"
valueFrom:
configMapKeyRef:
name: vote
key: option_b
image: wikitops/examplevotingapp-vote:1.1
imagePullPolicy: IfNotPresent
name: vote
ports:
- containerPort: 8080
name: vote
protocol: TCP
Configure the result Pods to use the result service account.
~/data/votingapp/14_serviceaccounts/result.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
name: result
namespace: voting-app
spec:
replicas: 1
selector:
matchLabels:
name: result
strategy:
rollingUpdate:
maxSurge: 1
maxUnavailable: 1
type: RollingUpdate
template:
metadata:
labels:
name: result
spec:
serviceAccountName: result
automountServiceAccountToken: false
containers:
- env:
- name: "POSTGRES_DB"
valueFrom:
secretKeyRef:
name: db
key: name
- name: "POSTGRES_NAME"
valueFrom:
secretKeyRef:
name: db
key: user
- name: "POSTGRES_PASSWORD"
valueFrom:
secretKeyRef:
name: db
key: password
image: wikitops/examplevotingapp-result:1.1
imagePullPolicy: IfNotPresent
name: result
ports:
- name: result
containerPort: 8080
Create the resources based on the previous yaml files definition.
kubectl create -f ~/data/votingapp/14_serviceaccounts/

External documentation

Those documentations can help you to go further in this topic :
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Module
Create
Get
Describe
Explain
Delete
Module exercise
External documentation