It seems that a server is not necessarily running as a daemon, e.g. X server. If I am not correct, please let me know.

Is a daemon necessarily a server? Is there a daemon which is not a server? I guess there are quite a few, and I am not sure if the init processes under sysvinit and systemd are such examples.


closed as unclear what you're asking by muru, JigglyNaga, RalfFriedl, Michael Homer, Sparhawk Dec 21 '18 at 10:56

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  • Thanks. I am using Linux only, so it is hard for me to relate – Tim Dec 19 '18 at 18:48
  • That may be easier to understand. – Tim Dec 19 '18 at 18:53

Anything that is performing a task without being requested to do so by a client. I.e. a daemon that is not serving clients.

I've recently played around with SSHGuard, a daemon that parses connection logs and that blocks abusive hosts. This is not a server.

The DHCP client daemon that many Unices runs variations of is not a server.

NTP is often implemented as a daemon that can function without being a server (only as a leaf node client).

  • fail2ban (similar to SSHGuard) and smartd (monitoring of S.M.A.R.T values) are two other examples that come to mind. – Zeta Dec 19 '18 at 18:56
  • acpid, mcelog, irqbalance, rngd, atd, and cronare all additional examples that come to mind. – Austin Hemmelgarn Dec 19 '18 at 20:15

I am moving Mark's comment here

https://www.tuhs.org//cgi-bin/utree.pl?file=V7/usr/src/cmd/update.c is a daemon that is not a server.

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