Clarify some details

exercises/10-distributed-builds/instructions.md

@@ -2,16 +2,25 @@
 
 You will start a VM using Vagrant as practice environment to set up a distributed build with 2 agents.
 
+## Starting up the VMs
+
+1. To start up the VMs, navigate to this directory. It should contain a `Vagrantfile`.
+2. Run the command `vagrant up`. Bringing up the VMs might take some minutes. The two VMs will be available with the IP address `192.168.99.201` and `192.168.99.202`. The username/password credentials for those VMs are `jenkins:jenkins`.
+
 ## 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 commands `useradd -d /var/lib/jenkins jenkins` and `passwd 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".
+3. 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 IP address `192.168.99.201` as host and provide credentials by selecting "Username with password". You will likely have to create a new credential. 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.
+5. Add one more agent with the IP address `192.168.99.202`.
 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.
+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.
+
+## Shutting down the VMs
+
+1. After you are done with the exercise, navigate to the directory containing the `Vagrantfile`.
+2. Tear down the VM by executing `vagrant destroy -f`.