Jenkins - j_acegi_security_check

You may have forgotten to select a Security Realm as specified below

https://wiki.jenkins-ci.org/display/JENKINS/Standard+Security+Setup

In case you have locked yourself out, you can revert the Jenkins config.xml file to set <useSecurity>true</useSecurity> node value to false by following instructions here

https://wiki.jenkins-ci.org/display/JENKINS/Disable+security

As mentioned on the bug page:

The error was caused by a proxy pass rule "/jenkins http://localhost:9080/jenkins/" which led to the incomming (jenkins) request "/jenkins//j_acegi_security_check" (double //). So the login page was rejected with 404 (while all other pages where served).

Make sure your /jenkins ProxyPass does not end with a trailing slash in the destination URL.

Spent ages wrestling with this one, make sure a Security Realm is set when you are choosing your Authorization method in Jenkins.

That is, in Manage Jenkins → Configure Global Security select an option in the Security Realm list.

For example: