Cannot start systemd service - linux

Question

I have a spring boot executable jar in a digital ocean droplet. I'm able to execute the jar using java -jar myapp.jar Now I want to have i run as a service.
I've created the file /etc/systemd/system/myapp.service with these contents
[Unit]
Description=myapp
After=syslog.target
[Service]
User=kevin
ExecStart=/var/myapp/myapp-backend-1.0-SNAPSHOT.jar
SuccessExitStatus=143
[Install]
WantedBy=multi-user.target
Then enabled it to start at system startup
systemctl enable myapp.service
I'm now attempting to start the service
systemctl start myapp.service
But I'm getting this error
Failed to start myapp.service: Unknown unit: myapp.service
See system logs and 'systemctl status myapp.service' for details.
running systemctl status myapp.service return this:
Failed to get properties: No such interface ''

Answer 1

Try this :
[Unit]
Description=myapp
After=syslog.target
[Service]
User=kevin
ExecStart=java -jar /var/myapp/myapp-backend-1.0-SNAPSHOT.jar
SuccessExitStatus=143
Restart=always
RestartSec=5
[Install]
WantedBy=multi-user.target
I have add :
java -jar in youre ExecStart
Restart=always => If java crack, systemd restart the service
RestartSec=5 => After crash the service restart avec 5 seconds
After youre modification, reload the systemd daemon :
systemctl daemon-reload
Enable on startup :
systemctl enable myapp.service
And start now :
systemctl start myapp.service

Answer 2

You need a wrapper script for the jar mentioned in ExecStart to handle start, stop and restart methods.
Extensive instructions and an example script can be found here