Pronounced "
dee-mun" as in the word for devil, as well as "
day-mun," a daemon is a Unix/Linux program that executes in the background ready to perform an operation when required. Functioning like an extension to the operating system, a daemon is usually an unattended process that is initiated at startup. Typical daemons are print spoolers and email handlers or a scheduler that starts up another process at a designated time. The term comes from Greek mythology, meaning "guardian spirit." See
agent and
mailer-daemon.