Type=

• https://www.freedesktop.org/software/systemd/man/systemd.service.html#Type=

simple, exec, forking, oneshot, dbus, notify, notify-reload or idle

configfs
binfmt_misc
fusectl
hugetlbfs
tracefs

oneshot is generally not recommended to use idle or oneshot for long-running services

ChatGPT yarn start example

[Unit]
Description=My Yarn Start Service
  
[Service]
Type=simple
ExecStart=/path/to/yarn start
WorkingDirectory=/path/to/project 

[Install] 
WantedBy=multi-user.target

Related

• /lib/systemd/system/
• .service

See also

• systemd, .service, /lib/systemd/system/, /etc/systemd/system/, Type=, systemctl list-units --type=service, systemctl daemon-reload, ExecStart, .timer, .mounts, .wants, .socket
• Systemd: systemctl, systemd-journald, journalctl systemd-cat, systemd-logind, systemd-networkd:networkctl, systemd-timesyncd, systemd-resolved, systemd-udevd , Systemd-logind: loginctl, hostnamectl, udevadm, systemd-run, portablectl, systemd-nspawn, systemd resource management, Timer (systemd), systemd logs, /etc/systemd/, systemd services, systemd-mount, /run/systemd/, .service, /usr/lib/systemd/, /usr/lib/systemd/system/, /usr/lib/systemd/system/systemd-resolved.service, /lib/systemd/, machinectl, systemd-oomd, systemd-analyze

https://wiki.ubuntu.com/DebuggingSystemd