Many people equate the word "daemon" with the word "demon", implying some kind of satanic connection between UNIX and the underworld. In the Unix System Administration Handbook Evi Nemeth states the following about daemons: In the general sense, daemon is an older form of the word "demon", from the Greek δαίμων. Maxwell's demon is consistent with Greek mythology's interpretation of a daemon as a supernatural being working in the background. Corbató, who worked on Project MAC in 1963, his team was the first to use the term daemon, inspired by Maxwell's demon, an imaginary agent in physics and thermodynamics that helped to sort molecules, stating, "We fancifully began to use the word daemon to describe background processes that worked tirelessly to perform system chores".
The term was coined by the programmers at MIT's Project MAC. Daemons such as cron may also perform defined tasks at scheduled times. Systems often start daemons at boot time that will respond to network requests, hardware activity, or other programs by performing some task. Such procedures are often implemented in various convenience routines such as daemon(3) in Unix. In addition, a daemon launched by forking and exiting typically must perform other operations, such as dissociating the process from any controlling terminal (tty). A daemon is usually created either by a process forking a child process and then immediately exiting, thus causing init to adopt the child process, or by the init process directly launching the daemon. In a Unix environment, the parent process of a daemon is often, but not always, the init process.
For example, syslogd is a daemon that implements system logging facility, and sshd is a daemon that serves incoming SSH connections. Traditionally, the process names of a daemon end with the letter d, for clarification that the process is in fact a daemon, and for differentiation between a daemon and a normal computer program. In multitasking computer operating systems, a daemon ( / ˈ d iː m ən/ or / ˈ d eɪ m ən/) is a computer program that runs as a background process, rather than being under the direct control of an interactive user. Components of some Linux desktop environments that are daemons include D-Bus, NetworkManager (here called unetwork), PulseAudio ( usound), and Avahi.
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