In Unix, all of the programs that are running in the background are called daemons. They usually have a name that ends with the letter d, like sshd or syslogd, and they provide many functionalities of the OS.
Beginning with daemons
Operating system support
In macOS, Unix, and Linux, a process is a daemon if it survives its parent life cycle, that is, when the parent process terminates its execution and the child process lives on. That's because the process parent is changed to the init process, a special daemon with no parent, and PID 1, which starts and terminates with the OS. Before going into this further, let's introduce two very important concepts – ...