Installed Jenkins 2.39 on Debian as per http://pkg.jenkins-ci.org/debian/. Opened it in browser (Firefox) and it's asking for credentials from the log file; copied and pasted that password but it doesn't work. Disabled useSecurity (and friends) in /var/lib/jenkins/config.xml, restarted Jenkins but to no avail: it still asks for password and it overwrites all changes to config.xml. The config.xml is clobbered even when chown'd to root and set to read-only (444) access. Any ideas how to get out of that hole?
UPDATE: apparently an obscure file has to be created in JENKINS_HOME directory with the contents 2 as described at this link. User friendliness at its peak.