systemd.service
freedesktop systemd.service
Description¶
A unit configuration file whose name ends in ".service" encodes information about a process controlled and supervised(监督) by systemd.
This man page lists the configuration options specific to this unit type. See systemd.unit(5) for the common options of all unit configuration files. The common configuration items are configured in the generic "[Unit]" and "[Install]" sections. The service specific configuration options are configured in the "[Service]" section.
总结：特定的的配置项和通用的配置项。
Additional options are listed in systemd.exec(5), which define the execution environment the commands are executed in（执行环节）, and in systemd.kill(5), which define the way the processes of the service are terminated(终止流程), and in systemd.resource-control(5), which configure resource control settings for the processes of the service.
If a service is requested under a certain name but no unit configuration file is found, systemd looks for a SysV init script by the same name (with the .service suffix removed) and dynamically creates a service unit from that script. This is useful for compatibility with SysV. Note that this compatibility is quite comprehensive but not 100%. For details about the incompatibilities, see the Incompatibilities with SysV document.
Service Templates¶
It is possible for systemd services to take a single argument via the "service@argument.service" syntax. Such services are called "instantiated" services, while the unit definition without the argument parameter is called a "template". An example could be adhcpcd@.service service template which takes a network interface as a parameter to form an instantiated service. Within the service file, this parameter or "instance name" can be accessed with %-specifiers. See systemd.unit(5) for details.
思考：上面这段话并没有搞清楚
Options¶
Service files must include a "[Service]" section, which carries information about the service and the process it supervises（监管）. A number of options that may be used in this section are shared with other unit types. These options are documented in systemd.exec(5), systemd.kill(5) and systemd.resource-control(5). The options specific to the "[Service]" section of service units are the following:
how to run a program as a service in systemd system
https://superuser.com/questions/1236961/running-an-executable-as-a-service-under-debian-8
https://www.tecmint.com/create-new-service-units-in-systemd/