root@xiakaibi-PC:~# service jenkins restart
Job for jenkins.service failed because the control process exited with error code.
See "systemctl status jenkins.service" and "journalctl -xe" for details.
root@xiakaibi-PC:~# systemctl status jenkins.service
● jenkins.service - LSB: Start Jenkins at boot time
Loaded: loaded (/etc/init.d/jenkins; generated; vendor preset: enabled)
Active: failed (Result: exit-code) since Tue 2019-09-17 16:52:59 CST; 1min 32s ago
Docs: man:systemd-sysv-generator(8)
Process: 28888 ExecStart=/etc/init.d/jenkins start (code=exited, status=1/FAILURE)
Sep 17 16:52:59 xiakaibi-PC systemd[1]: Starting LSB: Start Jenkins at boot time...
Sep 17 16:52:59 xiakaibi-PC jenkins[28888]: ERROR: No Java executable found in current PATH: /bin:/usr/bin:/sbin:/usr/sbi
Sep 17 16:52:59 xiakaibi-PC jenkins[28888]: If you actually have java installed on the system make sure the executable is
September 17 16:52:59 xiakaibi-PC systemd[1]: jenkins.service: Control process exited, code=exited status=1
September 17 16:52:59 xiakaibi-PC systemd[1]: Failed to start LSB: Start Jenkins at boot time.
September 17 16:52:59 xiakaibi-PC systemd[1]: jenkins.service: Unit entered failed state.
September 17 16:52:59 xiakaibi-PC systemd[1]: jenkins.service: Failed with result'exit-code'.
Solution
It means that the java file is not found, you need to copy the java file address by yourself
Open the etc/init.d/jenkins file, you can see that the path specified in the header does not include java_home. It should be the first time that the system reads the path when jdk is not installed. Modify the configuration and try again

Restart jenkins:
sudo service jenkins restart