# sudo vim /etc/sysconfig/jenkins
JENKINS_PORT="8081" // 8080 is default port
// JENKINS_PORT="81" -> I change port to 81 or 8X... and always cannot access Jenkins web page. Bug????
# sudo systemctl restart jenkins
Linux - Change Jenkins Port
Linux - Set Jenkins Login Security via Linux Account
Step 1. Add jenkins user to root group.
# vim /etc/group
root:x:0:jenkins
Step 2. Change shadow file permission.
# sudo chmod g+r /etc/shadow
# ls -la /etc
----r-----. 1 root root 966 Feb 4 14:41 shadow
