jenkins root user run

# lsb_release -a
No LSB modules are available.
Distributor ID:	Ubuntu
Description:	Ubuntu 20.04.4 LTS
Release:	20.04
Codename:	focal

# find / -name "jenkins"
/var/lib/jenkins
/var/cache/jenkins
/var/log/jenkins

chown -R root:root /var/lib/jenkins
chown -R root:root /var/cache/jenkins
chown -R root:root /var/log/jenkins

vim /etc/default/jenkins

#JENKINS_USER=$NAME
JENKINS_USER=root
#JENKINS_GROUP=$NAME
JENKINS_GROUP=root

vim /lib/systemd/system/jenkins.service

#User=jenkins
User=root
#Group=jenkins
Group=root

systemctl daemon-reload
systemctl restart jenkins.service