Daemon

[Juliano Nichols]

In multitasking computer operating systems, a daemon (/ˈdiːmən/ or /ˈdeɪmən/)[1] is a computer program that runs as a background process, rather than being under the direct control of an interactive user. 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. For example, .mw-parser-output .monospacedfont-family:monospace,monospacesyslogd is a daemon that implements system logging facility, and sshd is a daemon that serves incoming SSH connections.

In a Unix environment, the parent process of a daemon is often, but not always, the init process. 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 addition, a daemon launched by forking and exiting typically must perform other operations, such as dissociating the process from any controlling terminal (tty). Such procedures are often implemented in various convenience routines such as daemon(3) in Unix.

Systems often start daemons at boot time that will respond to network requests, hardware activity, or other programs by performing some task. Daemons such as cron may also perform defined tasks at scheduled times.

The term was coined by the programmers at MIT's Project MAC. According to Fernando J. Corbat, 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".[2] Unix systems inherited this terminology. Maxwell's demon is consistent with Greek mythology's interpretation of a daemon as a supernatural being working in the background.

A further characterization of the mythological symbolism is that a daemon is something that is not visible yet is always present and working its will. In the Theages, attributed to Plato, Socrates describes his own personal daemon to be something like the modern concept of a moral conscience: "The favour of the gods has given me a marvelous gift, which has never left me since my childhood. It is a voice that, when it makes itself heard, deters me from what I am about to do and never urges me on".[citation needed]

In a strictly technical sense, a Unix-like system process is a daemon when its parent process terminates and the daemon is assigned the init process (process number 1) as its parent process and has no controlling terminal. However, more generally, a daemon may be any background process, whether a child of the init process or not.

On a Unix-like system, the common method for a process to become a daemon, when the process is started from the command line or from a startup script such as an init script or a SystemStarter script, involves:

If the process is started by a super-server daemon, such as inetd, launchd, or systemd, the super-server daemon will perform those functions for the process,[7][8][9] except for old-style daemons not converted to run under systemd and specified as Type=forking[9] and "multi-threaded" datagram servers under inetd.[7]

On Microsoft Windows NT systems, programs called Windows services perform the functions of daemons. They run as processes, usually do not interact with the monitor, keyboard, and mouse, and may be launched by the operating system at boot time. In Windows 2000 and later versions, Windows services are configured and manually started and stopped using the Control Panel, a dedicated control/configuration program, the Service Controller component of the Service Control Manager (sc command), the net start and net stop commands or the PowerShell scripting system.

On the classic Mac OS, optional features and services were provided by files loaded at startup time that patched the operating system; these were known as system extensions and control panels. Later versions of classic Mac OS augmented these with fully fledged faceless background applications: regular applications that ran in the background. To the user, these were still described as regular system extensions.

macOS, which is a Unix system, uses daemons but uses the term "services" to designate software that performs functions selected from the Services menu, rather than using that term for daemons, as Windows does.

The Ancient Greek: δαίμων, pronounced daimon or daemon (meaning "god", "godlike", "power", "fate"),[1][2] originally referred to a lesser deity or guiding spirit such as the daimons of ancient Greek religion and mythology and of later Hellenistic religion and philosophy.[3] The word is derived from Proto-Indo-European daimon "provider, divider (of fortunes or destinies)," from the root *da- "to divide".[4] Daimons were possibly seen as the souls of men of the golden age acting as tutelary deities, according to entry δαίμων at Liddell & Scott.[5] See also daimonic: a religious, philosophical, literary and psychological concept.

One tradition of Greek thought, which found agreement in the mind of Plato, was of a daimon which existed within a person from their birth, and that each individual was obtained by a singular daimon prior to their birth by way of lot.[6]

Regarding the charge brought against Socrates in 399, Plato surmised "Socrates does wrong because he does not believe in the gods in whom the city believes, but introduces other daemonic beings..." Burkert notes that "a special being watches over each individual, a daimōn who has obtained the person at his birth by lot, is an idea which we find in Plato, undoubtedly from earlier tradition. The famous, paradoxical saying of Heraclitus is already directed against such a view: 'character is for man his daimon'".[6]

A distorted view of Homer's daemon results from an anachronistic reading in light of later characterizations by Plato and Xenocrates, his successor as head of the Academy, of the daemon as a potentially dangerous lesser spirit:[6][20] Burkert states that in the Symposium, Plato has "laid the foundation" that would make it all but impossible to imagine the daimon in any other way with Eros, who is neither god nor mortal but a mediator in between, and his metaphysical doctrine of an

Daemons scarcely figure in Greek mythology or Greek art: they are felt, but their unseen presence can only be presumed,[citation needed] with the exception of the agathodaemon, honored first with a libation in ceremonial wine-drinking, especially at the sanctuary of Dionysus, and represented in iconography by the chthonic serpent.Burkert suggests that, for Plato, theology rests on two Forms: the Good and the Simple; which "Xenocrates unequivocally called the unity god" in sharp contrast to the poet's gods of epic and tragedy.[6] Although much like the deities, these figures were not always depicted without considerable moral ambiguity:

In the Archaic or early Classical period, the daimon had been democratized and internalized for each person, whom it served to guide, motivate, and inspire, as one possessed of such good spirits.[citation needed] Similarly, the first-century Roman imperial cult began by venerating the genius or numen of Augustus, a distinction that blurred in time.

However, each time I start up Ubuntu, Dropbox pops up the window saying "Dropbox is the easiest way to share ... you must download proprietary daemon ..." This is the same window that appeared during the installation, which had been 100% completed since. Each time I click OK, the daemon gets installed without problem and Dropbox works fine.

Without clicking OK and re-downloading the daemon, Dropbox icon will not show up in Ubuntu system bar. It is annoying to have to redo this process every time I start my computer. Could someone help me with this? Thanks.

Having said that and as I'd really like to help with this, would you mind trying an advanced reinstall using this installer to see if this will fix your problem? In the meantime, you may also want to review this Help Center article too.

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This is happening to me very frequently now, on multiple computers running linux mint 19. I have followed the instructions noted in this thread multiple times as well- it fixes the issue for a few days, but then like bad magic its starts doing it again.

The -i option "auto installs dropboxd if not available on the system". Could this switch be malfunctioning, erroneously thinking that the daemon is not there, and be part of the cause of this issue? I'm not sure why the -i option is needed after dropbox has been installed anyway, but maybe it is needed for some reason.

The other thing to note is that whenever I get this installation pop-up prompt, dropbox is actually already running and the icon is showing in my tray. So regardless of whether I get this installation prompt or not, dropbox always starts up anyway and is already running, apparently in parallel to, and independent of, whatever check is being made that results in the prompt to re-install the sw. If I accept the prompt to re-download the sw, it does so and then invokes a second instance of dropbox and they both run side by side, with two icons in the tray. I can use dropbox with both instances, or a i can kill off one of the instances and continue. Very strange. I never let more than one instance run very long if I notice it because I doubt that is a good thing to let persist very long.

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