If the security configurations for Jenkins is not proper, there may be a chance to get admin user locked out.
This article explains the steps to recover Jenkins admin login by disabling the security authorization.
Step1: Login to the Jenkins instance via ssh.
Step2: Stop Jenkins service.
#systemctl stop jenkins
Step3: Change the location to Jenkins home directory.
Step4: Open the Jenkins configuration file.
Step5: Update the following line and save.
Step6: Remove the elements authorizationStrategy and securityRealm from the same file and save.
Step7: Start Jenkins service.
#systemctl start jenkins
Step8: Now we can login to the Jenkins web console without any authorization and reset the admin user password as well as complete the security configurations.