One may “accidentally” set up security realm / authorization in such a way that you may no longer able to reconfigure Jenkins.
When this happens, you can fix this by the following steps:
- Stop Jenkins (the easiest way to do this is to kill the servlet container.)
- Go to $JENKINS_HOME in the file system and find config.xml file.
- Open this file in the editor.
- Look for the <useSecurity>true</useSecurity> element in this file.
- Replace true with false
- Start Jenkins
When Jenkins comes back, it’s in the unsecured mode where everyone gets full access to the system.
[Seen: Jenkins wiki]