<p>I'm using Jenkins deployed on Kubernetes. Jenkins pods are deployed in 'kubernetes-plugin' namespace, and uses service account 'jenkins', which is defined below:</p>

<pre><code>---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: jenkins

---
kind: Role
apiVersion: rbac.authorization.k8s.io/v1beta1
metadata:
  name: jenkins
rules:
- apiGroups: [""]
  resources: ["pods"]
  verbs: ["create","delete","get","list","patch","update","watch"]
- apiGroups: [""]
  resources: ["pods/exec"]
  verbs: ["create","delete","get","list","patch","update","watch"]
- apiGroups: [""]
  resources: ["pods/log"]
  verbs: ["get","list","watch"]
- apiGroups: [""]
  resources: ["secrets"]
  verbs: ["get"]
- apiGroups: ["", "extensions", "apps"]
  resources: ["deployments", "replicasets", "pods"]
  verbs: ["*"]
---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: RoleBinding
metadata:
  name: jenkins
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: Role
  name: jenkins
subjects:
- kind: ServiceAccount
  name: jenkins
</code></pre>

<p>But when I use <code>kubectl apply -f web-api-deploy.yaml -n default</code> in the jenkins pipeline, it report the following error:</p>

<pre><code>deployments.extensions "news-app-web-api-dev" is forbidden: User "system:serviceaccount:kubernetes-plugin:jenkins" cannot get deployments.extensions in the namespace "default"
</code></pre>

<p>which means: you cannot deploy on namespace 'default' when using service account 'jenkins' in namespace 'kubernetes-plugin'</p>

<p>So is there a way to deploy a deployment in another namespace?? How.</p>

<blockquote>
  <p>So is there a way to deploy a deployment in another namespace?? How.</p>
</blockquote>

<p>If I'm not mistaken, <a href="https://github.com/jenkinsci/kubernetes-plugin" rel="nofollow noreferrer">this github project</a> gives steps to run in different namespace. It all boils down to this:</p>

<p>You need to craete ServiceAccount, Role and RoleBinding in different namespace and use it like noted in documentation. Here is relevant part:</p>

<pre><code>Ensure you create the namespaces and roles with the following commands,
then run the tests in namespace kubernetes-plugin with the service account
jenkins (edit src/test/kubernetes/service-account.yml to use a different 
service account)

kubectl create namespace kubernetes-plugin-test
kubectl create namespace kubernetes-plugin-test-overridden-namespace
kubectl create namespace kubernetes-plugin-test-overridden-namespace2
kubectl apply -n kubernetes-plugin-test -f src/main/kubernetes/service-account.yml
kubectl apply -n kubernetes-plugin-test-overridden-namespace -f src/main/kubernetes/service-account.yml
kubectl apply -n kubernetes-plugin-test-overridden-namespace2 -f src/main/kubernetes/service-account.yml
kubectl apply -n kubernetes-plugin-test -f src/test/kubernetes/service-account.yml
kubectl apply -n kubernetes-plugin-test-overridden-namespace -f src/test/kubernetes/service-account.yml
kubectl apply -n kubernetes-plugin-test-overridden-namespace2 -f src/test/kubernetes/service-account.yml
</code></pre>

<p>Also applicable to your situation is to create new Role and RoleBinding in default namespace referencing jenkins ServiceAccount from kubernetes-plugin namespace like so:</p>

<pre><code>kind: Role
apiVersion: rbac.authorization.k8s.io/v1beta1
metadata:
  name: role-jenkins-default
  namespace: default
rules:
- apiGroups: [""]
  resources: ["pods"]
  verbs: ["create","delete","get","list","patch","update","watch"]
- apiGroups: [""]
  resources: ["pods/exec"]
  verbs: ["create","delete","get","list","patch","update","watch"]
- apiGroups: [""]
  resources: ["pods/log"]
  verbs: ["get","list","watch"]
- apiGroups: [""]
  resources: ["secrets"]
  verbs: ["get"]
- apiGroups: ["", "extensions", "apps"]
  resources: ["deployments", "replicasets", "pods"]
  verbs: ["*"]
---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: RoleBinding
metadata:
  name: roleb-jenkins-default
  namespace: default
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: Role
  name: role-jenkins-default
subjects:
- kind: ServiceAccount
  name: jenkins
  namespace: kubernetes-plugin
</code></pre>

<p>Note that <code>role-</code> and <code>roleb-</code> prefixes as well as <code>-deault</code> suffix are added to name for clarity. Same goes for explicitly listing namespace <code>default</code> for easier bookkeeping and clarity.</p>

<p>This change should get you past by the error mentioned in your question.</p>
