I installed jenkins on Cnetos 7 using the following:
sudo wget -O /etc/yum.repos.d/jenkins.repo http://pkg.jenkins.io/redhat-stable/jenkins.repo sudo rpm --impor
In my case I were starting jenkins service from root instead of jenkins user
i did
sed -i 's/JENKINS_USER="jenkins"/JENKINS_USER="root"/g /etc/sysconfig/jenkins
then
service jenkins restart
all work well