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+# Key CI/CD/Jenkins Concepts and their Usage
+
+## Using the REST API for common operations
+
+1. Create a new user named `buildbot`.
+2. Add adminstration permissions for the user.
+3. Log in with user `buildbot`.
+4. Generate the API token for the user.
+5. Generate a Jenkins crumb from the command line.
+6. Export the environment variables `JENKINS_CRUMB` and `JENKINS_API_TOKEN` with the correct values.
+7. Trigger a build of the job `gradle-initializr` with a `curl` command using the REST API.
+8. Disable the job `gradle-initializr` with a `curl` command using the REST API.
+9. Reenable the job `gradle-initializr` with a `curl` command using the REST API.
+10. Download the Jenkins CLI client.
+11. Trigger the build of the job `gradle-initializr` with a `curl` command using the Jenkins CLI.
+
+<details><summary>Show Solution</summary>
+<p>
+
+Create the new user.
+
+![Create User](./images/09-rest-api/create-user.png)
+
+Add user permissions.
+
+![User Permissions](./images/09-rest-api/user-permissions.png)
+
+Generate the API token.
+
+![API Token](./images/09-rest-api/api-token.png)
+
+Generate the Jenkins crumb from the CLI.
+
+```bash
+$ curl -u "buildbot:pwd" 'http://localhost:8080/crumbIssuer/api/xml?xpath=concat(//crumbRequestField,":",//crumb)'
+Jenkins-Crumb:890d0b4c9c1b111deb55b196813a0ae1
+$ export JENKINS_CRUMB=Jenkins-Crumb:890d0b4c9c1b111deb55b196813a0ae1
+$ export JENKINS_API_TOKEN=11e2f3c68399b6bc3a28bc06e002be104d
+```
+
+Trigger a build with the `curl` command.
+
+```bash
+$ curl -X POST -H "$JENKINS_CRUMB" http://buildbot:$JENKINS_API_TOKEN@localhost:8080/job/gradle-initializr/build
+```
+
+Disable the job via the REST API. You will see that the job indicated its status.
+
+```bash
+$ curl -X POST -H "$JENKINS_CRUMB" http://buildbot:$JENKINS_API_TOKEN@localhost:8080/job/gradle-initializr/disable
+```
+
+![Disabled Job](./images/09-rest-api/disabled-job.png)
+
+Reenable the job.
+
+```bash
+$ curl -X POST -H "$JENKINS_CRUMB" http://buildbot:$JENKINS_API_TOKEN@localhost:8080/job/gradle-initializr/enable
+```
+
+Download the Jenkins URL by calling the URL `localhost:8080/jnlpJars/jenkins-cli.jar` from the browser.
+
+In the terminal, navigate to the directory that contains the Jenkins CLI JAR file. Use the Jenkins CLI to trigger a build with the correct command. This simply provide the password instead of the API token.
+
+```bash
+$ java -jar jenkins-cli.jar -s http://localhost:8080 -auth buildbot:pwd build gradle-initializr
+```
+
+
+
+</p>
+</details>
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