jenkins: Run Jenkins in Kubernetes

Running Jenkins in Kubernetes is relatively straightforward.  The
Kubernetes plugin automatically discovers all the connection and
authentication configuration, so a `kubeconfig` file is no longer
necessary.  I did set the *Jenkins tunnel* option, though, so that
agents will connect directly to the Jenkins JNLP port instead of going
through the ingress controller.

Jobs now run in pods in the *jenkins-job* namespace instead of the
*jenkins* namespace.  The latter is now where the Jenkins controller
runs, and the controller should not have permission to modify its own
resources.

jenkins/README.md

@@ -1,38 +1,31 @@
-# Jenkins Kubernetes Integration
+# Jenkins in Kubernetes
 
 ## Kubernetes Setup
 
-Create *jenkins* user:
-
-```sh
-kubeadm kubeconfig user \
-    --client-name jenkins \
-    --config kubeadm-user.yaml \
-    --org jenkins \
-    > jenkins.kubeconfig
-```
-
 Configure Jenkins resources:
 
 ```sh
-kubectl apply -f jenkins.yaml
+ln imagepull-gitea jenkins/.dockerconfigjson
+kubectl apply -k jenkins
 ```
 
-
 ## Jenkins Setup
 
 Install [Kubernetes plugin][0].
 
 Set *TCP port for inbound agents* setting (*Manage Jenkins* → *Configure Global
-Security*) to *Fixed* and enter a number.  Be sure to open this port with
-*firewalld* on the Jenkins server.
+Security*) to *Fixed* and enter `40414`.
 
 Configure Kubernetes (*Manage Jenkins* → *Manage Nodes and Clouds* → *Configure
 Clouds*:
 
-* *Kubernetes URL*: https://kubernetes.pyrocufflink.blue:6443
-* *Kubernetes server certificate key*: Contents of `/etc/kubernetes/pki/ca.crt`
-* *Kubernetes Namespace*: jenkins
-* *Credentials*: Certificate and private key from `jenkins.kubeconfig`
+1. *Add a new cloud* → *Kubernetes*
+2. Enter a name
+3. *Kubernetes Cloud details...*
+   * *Kubernetes URL*: (leave blank; will use Kubernetes service discovery)
+   * *Kubernetes Namespace*: `jenkins-jobs`
+   * *Credentials*: `- none -` (will use Service Account token)
+   * *Jenkins tunnel*: `jenkins.jenkins.svc.cluster.local:` (trailing colon!)
+
 
 [0]: https://plugins.jenkins.io/kubernetes/