What Is Service on Linux?
There is a term service which is similar to the daemon. Services are processes that usually run in the background and respond to requests from other processes running on the same system or processes connected via a network. Many services usually run as daemons.
A service can call another service without any human input. After a service calls another service, those services can interact with each other automatically (without any human intervention). How a service behaves is determined by its configuration file. On Linux OS, it is usually saved as a unit file in a certain directory under /usr/lib/systemd/system or /etc/systemd/system. Details will be explained in the next section.
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