A SERVICE file is a service unit file included with systemd, an init (initialization) system used by various Linux distributions to bootstrap user space and manage processes. It contains information about how to manage a server application or service, including how to start or stop the service and when it should be automatically started.

systemd init system is a suite of programs included in various Linux distributions. The system is used to manage different aspects of a server. A unit is a resource that systemd can operate and manage. Each unit has a configuration file known as a unit file. The suffix of the unit file indicates for which type of unit the file is storing configuration information. systemd unit files are located in the following directory by default: /lib/systemd/system systemd unit files created or customized by the system administrator are located in the following directory: /etc/systemd/system/ If you want to edit the SERVICE unit file do not directly edit the SERVICE file in the directory. Instead, you should copy the file, edit the copy, then override the original SERVICE file. NOTE: systemd is booted by many Linux distributions, including Red Hat, Arch Linux, Fedora, CentOS, Ubuntu, Mageia, CoreOS, and Alpine Linux.