Create a file example.service

sudo vim /etc/systemd/system/example.service

Into this file configure:

[Unit]
Description=Service description
After=network.target

[Service]
WorkingDirectory=/path/to/your/directory
ExecStart=<command>
Restart=on-failure

[Install]
WantedBy=multi-user.target

For example in my case I want to run in my local machine a frontend

WorkingDirectory=/my/path/project/directory
ExecStart=/usr/local/bin/yarn start:dev

In my case I didn’t know the path of yarn application. I could find it with: which yarn.