Why did Jenkins tell me to upgrade to Hudson?

I have the latest version of Jenkins, and I launched it with "java -jar jenkins.jar." Then I got an error

????: Failed Loading plugin rest-plugin hudson.util.IOException2: Unable to create instance of org.hudsonci.rest.plugin.RestPlugin from rest-plugin

After that, when I visit Jenkins at localhost:8080, Jenkins shows "New version of Jenkins (2.1.0) is available", and download link to Hudson.war 2.1.0**

Did the Jenkins merge back into Hudson? As far as I know, most people are sayin开发者_StackOverflowg Jenkins will be better than Hudson.

Is there anybody that knows what happened?

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It sounds like what happened is this: you kept your old settings when you upgraded to Jenkins. This included the update URL, so Jenkins is polling the old Hudson url for updates. Once you fix this, you should be golden. To fix it, just do this:

Under Manage Jenkins, go to Manage Plugins and click on the advanced tab. Make sure that the Update URL is set to http://updates.jenkins-ci.org/update-center.json