• create the config (?) for the service as /lib/systemd/system/<unit name>.service
  • is it actually supposed to go in /etc/systemd/system not /lib/systemd/system?
• Inside the config:
• enable the service: sudo systemctl enable application.service

Restart Always in service has limits. Kill 'em limits:

• in [unit] add StartLimitIntervalSec=0 so systemd will continue to try to restart the service forever
• in [Service] add RestartSec=1 to have systemd retry every second (instead of the default every 100ms)

• plug in the usb device look up the vender id and product id of the USB device. lsusb or usbreset will both give you this information
• create a file in /etc/udev/rules.d for example /etc/udev/rules.d/80-local.rules and put in it something like this example:

ACTION=="add", ATTR{idVendor}=="0582", ATTR{idProduct}=="01d6", TAG+="systemd", ENV{SYSTEMD_WANTS}="jackd.service"

source

Example

• create /etc/udev/rules.d/20-usb-bus.rules with content: KERNEL=="usb[1-2]", TAG+="systemd"
• reboot or udev rules reload and now voila: systemctl status dev-bus-usb-001-001.device
• then in [Unit] you can do something like After=dev-bus-usb-001-001.device dev-bus-usb-002-001.device

source

• https://www.digitalocean.com/community/tutorials/how-to-use-systemctl-to-manage-systemd-services-and-units
• https://wiki.archlinux.org/index.php/systemd#Handling_dependencies
• systemd for upstart users (16.04)
• getting lists of systemd services (enabled, running, etc.)
• how systemd runs an upstart service (example with Mosquitto)
• automatically start one service after another is started