kubernetes-handbook/concepts/serviceaccount.md

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Service Account

Service account是为了方便Pod里面的进程调用Kubernetes API或其他外部服务它不同于User account

  • User account是为人设计的而service account则是为了Pod中的进程

  • User account是跨namespace的而service account则是仅局限它所在的namespace

  • 开启ServiceAccount默认开启每个namespace都会自动创建一个Service account并会相应的secret挂载到每一个Pod中

    • 默认ServiceAccount为default自动关联一个访问kubernetes API的Secret
    • 每个Pod在创建后都会自动设置spec.serviceAccount为default除非指定了其他ServiceAccout
    • 每个container启动后都会挂载对应的token和ca.crt/var/run/secrets/kubernetes.io/serviceaccount/

    当然了也可以创建更多的Service Account

$ cat > /tmp/serviceaccount.yaml <<EOF
apiVersion: v1
kind: ServiceAccount
metadata:
  name: build-robot
  namespace: default
EOF
$ kubectl create -f /tmp/serviceaccount.yaml
serviceaccounts/build-robot

Service Account为服务提供了一种方便的认知机制但它不关心授权的问题。可以配合RBAC来为Service Account鉴权

  • 配置--authorization-mode=RBAC--runtime-config=rbac.authorization.k8s.io/v1alpha1
  • 配置--authorization-rbac-super-user=admin
  • 定义Role、ClusterRole、RoleBinding或ClusterRoleBinding

比如

# This role allows to read pods in the namespace "default"
kind: Role
apiVersion: rbac.authorization.k8s.io/v1alpha1
metadata:
  namespace: default
  name: pod-reader
rules:
  - apiGroups: [""] # The API group "" indicates the core API Group.
    resources: ["pods"]
    verbs: ["get", "watch", "list"]
    nonResourceURLs: []
---
# This role binding allows "default" to read pods in the namespace "default"
kind: RoleBinding
apiVersion: rbac.authorization.k8s.io/v1alpha1
metadata:
  name: read-pods
  namespace: default
subjects:
  - kind: ServiceAccount # May be "User", "Group" or "ServiceAccount"
    name: default
roleRef:
  kind: Role
  name: pod-reader
  apiGroup: rbac.authorization.k8s.io