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When you uninstall a plugin in Jenkins, its configuration remains in existing jobs. Jenkins’s Manage Old Data feature helps you locate and remove these orphaned settings to prevent unexpected behaviors.

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1. Leftover Plugin Configuration

Even after removing the Copy Artifact plugin, job XML still holds references to it: 
<project>
  <builders>
    <hudson.plugins.copyartifact.CopyArtifact plugin="copyartifact">
      <project>ascii-build-job</project>
      <filter>advice.json</filter>
      <selector class="hudson.plugins.copyartifact.StatusBuildSelector"/>
    </hudson.plugins.copyartifact.CopyArtifact>
    <hudson.tasks.Shell>
      <command>ls advice.json && cat advice.json | jq -r .slip.advice > advice.message && \
[ $(wc -w &lt; advice.message) -gt 5 ] && echo "Advice - $(cat advice.message) has more than 5 words" && exit 1</command>
    </hudson.tasks.Shell>
  </builders>
</project>
Reinstalling the plugin simply re-enables this existing configuration without warning.

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2. Accessing the Manage Old Data Page

  1. Navigate to Manage Jenkins → Troubleshooting → Manage Old Data.
  2. Refresh the page. If Jenkins finds no outdated configurations, you’ll see:
The image shows a Jenkins interface on the "Manage Old Data" page, indicating that no old data was found. The sidebar includes options like "Build History" and "Manage Jenkins."
  1. Restart Jenkins to force detection of stale plugin entries.

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3. Detecting Unreadable Data

After the restart, return to Manage Old Data. Now Jenkins lists entries like CannotResolveClassException for missing plugins:
The image shows a Jenkins interface with a "Manage Old Data" section, listing unreadable data entries with errors related to "CannotResolveClassException."
Unreadable entries indicate XML blocks pointing to plugins that no longer exist. These must be discarded to clean up job configs.

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4. Discarding Unreadable Data

  1. Click Discard Unreadable Data.
  2. Confirm the prompt to remove all XML fragments referencing the deinstalled plugin.
Discarding is irreversible. Ensure you’ve backed up your job configurations before proceeding.

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5. Verifying Cleanup

  1. Trigger a build of ascii-build-job.
  2. Then run ascii-test-job.
Before cleaning workspaces, you may still see the old artifact: 
+ ls advice.json
advice.json
+ cat advice.json | jq -r .slip.advice
Don't try and bump start a motorcycle on an icy road.
+ wc -w < advice.message
11
+ [ 11 -gt 5 ]
+ echo "Advice - Don't try and bump start a motorcycle on an icy road. has more than 5 words"
Advice - Don't try and bump start a motorcycle on an icy road. has more than 5 words

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Cleaning Up Local Workspaces

Remove any leftover files on the Jenkins controller:
Job NameWorkspace PathCleanup Command
ascii-build-job/var/lib/jenkins/workspace/ascii-build-jobrm -rf /var/lib/jenkins/workspace/ascii-build-job
ascii-test-job/var/lib/jenkins/workspace/ascii-test-jobrm -rf /var/lib/jenkins/workspace/ascii-test-job
rm -rf /var/lib/jenkins/workspace/ascii-build-job
rm -rf /var/lib/jenkins/workspace/ascii-test-job
Re-run both jobs. Now ascii-test-job will fail because advice.json no longer exists: 
$ ls advice.json
ls: cannot access 'advice.json': No such file or directory

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Conclusion

Uninstalling a Jenkins plugin does not automatically purge its configurations. Use Manage Jenkins → Troubleshooting → Manage Old Data to detect and discard stale plugin data. For a complete reset, clean up any residual workspaces on the controller.

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