What is the file extension used for target files in systemd?

In systemd, target files are utilized to group together and control the startup of other units. The file extension used for these target files is .target. These files define a target state for the system, which can include pooling together different services, sockets, mount points, and other components that should be started or stopped in unison.

This organization allows for better management of services during the boot process and can simplify dependency handling among various system components. For instance, when you boot into a specific target, such as the default.target or multi-user.target, systemd understands to start all units associated with that target, enabling the system or service to reach the desired operational state.

The other types of files mentioned, such as .service, .socket, and .slice, serve specific purposes within the systemd framework but are focused on other areas of service management and resource control. .service files define individual services, .socket files manage socket-based communication, and .slice files are used for resource management and grouping. Each extension serves a distinct role, but for defining a target state in systemd, the correct file extension is indeed .target.