Write up description and add images

09-rest-api.md

@@ -66,7 +66,5 @@ In the terminal, navigate to the directory that contains the Jenkins CLI JAR fil
 $ java -jar jenkins-cli.jar -s http://localhost:8080 -auth buildbot:pwd build gradle-initializr
 ```
 
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 </p>
 </details>

10-distributed-builds.md

@@ -0,0 +1,49 @@
+# Key CI/CD/Jenkins Concepts and their Usage
+
+## Configuring and executing jobs in a distributed build
+
+1. Go to "Manage Jenkins" > "Manage Nodes". You should see a single `master` node.
+2. Configure the `master` node by setting the # of executor value to 0. That will take care of never using the `master` for job workload.
+3. Have other physical or virtual machines ready that can act as agent nodes. Log into the machine as `root` user and create a new user named `jenkins` with the command `useradd -d /var/lib/jenkins jenkins`. From the `master` node, copy the contents of the `id_rsa.key` file to the clipboard. Paste the contents of the clipboard to the file `/var/lib/jenkins/.ssh/authorized_keys`.
+4. Add new nodes by clicking "New Nodes". Enter an appropriate name and select the option "Permanent Agent". Use the remote directory `/home/jenkins/jenkins_slave` and set the # of executors to 2. Enter the host and provide credentials by selecting "SSH Username with private key". To keep things easy select "Non verifying Verification Strategy".
+4. Trigger a build. You should see that the build is only executed on the agent and not the `master` node.
+5. Add at least one more agent.
+6. Trigger a build. You should see that the build can be executed on any of the agents.
+7. Configure one of the agents to only build jobs with a specific label e.g. `java`. Change the "Usage" field to "Only build jobs with label expressions matching this node".
+8. Configure the `gradle-initializr` job and assign the label `java`.
+9. Trigger a build of the `gradle-initializr` job. It is only executed by the dedicated agent.
+10. Trigger other jobs that do not have the label `java` assigned to them. They are waiting for an agent that can execute the build.
+
+<details><summary>Show Solution</summary>
+<p>
+
+Configure the `master` node.
+
+![Master Configuration](./images/10-distributed-builds/master-config.png)
+
+Add a new agent node.
+
+![Agent Configuration](./images/10-distributed-builds/agent-config.png)
+
+You will see that the `master` node isn't even listed anymore in the executor overview.
+
+![Node Overview](./images/10-distributed-builds/node-overview.png)
+
+Reconfigure the agent node to only build jobs with a specific label.
+
+![Agent Label Configuration](./images/10-distributed-builds/agent-label-config.png)
+
+Reconfigure the job to only use agents that can handle a specific label.
+
+![Job Label Configuration](./images/10-distributed-builds/job-label-config.png)
+
+A build of the job is now only handled by an agent with the assigned label.
+
+![Build For Labeled Agent](./images/10-distributed-builds/build-for-label.png)
+
+Other jobs sit in a queue waiting for an agent that can handle the execution criteria.
+
+![Build For Labeled Agent](./images/10-distributed-builds/queued-job.png)
+
+</p>
+</details>