Added systemd service

Makefile

-all:
+all: jenkins-service
 	install -v -m755 -d /opt/jenkins
 	install -v -m644 -T jenkins-2.235.1.war /opt/jenkins/jenkins.war
+	install -v -m755 -d /var/cache/jenkins
+	install -v -m755 -d /var/lib/jenkins
+	install -v -m755 -d /var/log/jenkins
+	@echo "$$JENKINS_SERVICE" > /lib/systemd/system/jenkins.service
+	systemctl enable jenkins.service
 
 agent:
 	install -v -m755 -d /opt/jenkins
 	unzip -p jenkins-2.235.1.war WEB-INF/lib/remoting* > /opt/jenkins/agent.jar
+
+jenkins-service:
+define JENKINS_SERVICE
+[Unit]
+Description=Jenkins Continous Integration Server
+After=network-online.target
+Wants=network-online.target
+
+[Service]
+Type=simple
+User=root
+Group=root
+ExecStart=/opt/jdk/bin/java -Dcom.sun.akuma.Daemon=daemonized -Djava.awt.headless=true -Xmx1536m -DJENKINS_HOME=/var/lib/jenkins -jar /opt/jenkins/jenkins.war --logfile=/var/log/jenkins/jenkins.log --webroot=/var/cache/jenkins/war --daemon --httpPort=80 --handlerCountMax=100 --handlerCountMaxIdle=20 --accessLoggerClassName=winstone.accesslog.SimpleAccessLogger --simpleAccessLogger.format=combined --simpleAccessLogger.file=/var/log/jenkins/access_log
+Restart=on-failure
+
+[Install]
+WantedBy=multi-user.target
+endef
+export JENKINS_SERVICE