Talk:Daemon (computer software)

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The acronym expansion appears to be an urban legend. This query:

The first daemon (an abbreviation for Disk And Executive MONitor) was a program that automatically made tape backups of the file system. Does this sound about right? Any corrections or additions? Thank you for your time!

to Fernando J. Corbato, head of the CTSS project where the word entered the computer lexicon, prompted the following reply:

Your explanation of the origin of the word daemon is correct in that my group began using the term around that time frame. However the acronym explanation is a new one on me.

The page (it's in the article) which has this also notes that:

Professor Jerome H. Saltzer, who also worked on Project MAC, confirms the Maxwell's demon explanation.

So I'd say this one is pretty definitively "busted"! Noel (talk) 17:19, 18 Nov 2004 (UTC)

How is it busted? It would only be busted if Corbato had provided the actual etymology; instead it only remains unproven. --148.84.19.92

I found the article, and Corbato also says it's from Maxwell. See [1]. Beinsane 21:43, 15 Apr 2005 (UTC)

It will be of a great help if someone points to HOW to build the "daemon" applictaions here, with elementary examples.

Under any Unix or GNU system, just call the daemon(3) function.
Teddy 80087 07:17, 17 Jul 2004 (UTC)

Contents

[edit] phantom

who the heck calls a daemon a phantom? --Eean 01:15, 2 Jan 2005 (UTC)

ditto --148.84.19.92

[edit] Correct pronunciation?

Anybody want to venture a pronunciation guide? My understanding is that the original CTSS folks pronounced it "de'men", like the mythical creature. Most of the younger folks I know use "day'men", presumably because that's how it "looks" like it should be pronounced.

JohnH 18:35, 30 August 2005 (UTC)

It is pronounced exactly like the equivalent word demon (i.e., deeˡ-men). The more recent pronunciation is due to illiteracy. See Æ for details. - Loadmaster 14:31, 18 August 2006 (UTC)

Too many young kids have now watched too much STNG and its Ferengi daimons ;-).
Atlant 16:21, 18 August 2006 (UTC)
The Æ article says that in Classical Latin, the digraph was pronounced like "eye." I don't know anybody, young or old, who pronounces "daemon" like "diamond" without the D! MFNickster 01:24, 3 December 2006 (UTC)

I've done the IPA, and based on researches and the above have gone the "dee" route, changing what was on the page. --Slp1 03:18, 6 February 2007 (UTC)

[edit] Popular type of daemons

[edit] "Services"

I'm confused by the following (from paragraph six)...

"On Microsoft Windows systems, programs called "services" perform the functions of daemons, ..." "There are "services" as well, but these are completely different in concept."

Was the second "services" referencing something on the Mac?

In Windows programs running in the background (ie. similar to daemons under Unix) are called "services".
In Unix, some daemons will provide network-*services*... like provide mail-services (SMTP, POP) or web-services (HTTP) - where "service" refers to the ability to handle some network-protocol (achived by having a daemon understanding the protocol listning on the port that protocl uses).
So in Unix "service" refers to what the program (daemon) provides, while it in Windows (also) refers to the actual program (of course many Windows "services" thus doesn't provide any services (as understood in Unix) at all, as they do other things than understanding network-protocols).
koppe Tuesday 20 March 2007, 16:40 (CET)

[edit] Mailer-Daemon

How about the infamous mailer-daemon, folks???? Lots of people don't know what that is.

[edit] poor processes

A daemon kills the parent and forces the orphan to become adopted. Sounds like an appropriate name.

[edit] Here be dragons

Thought I'd mention FWIW that Harley Hahan (in his modest book entitled Harley Hahn's Student Guide To Unix claims that daemons are actually and originally a subset of "dragons", the difference being that dragons run automatically in the background, waiting for something to happen; daemons act the same, but must be manually invoked/started. --Gwern (contribs) 20:02 8 January 2007 (GMT)

[edit] parent process

The article states "Daemons typically do not have any existing parent process, but reside directly under init in the process hierarchy (PPID=1)" so the net result is that "init" is the parent process.

On all the unix systems I have seen, "init" is a real process, consuming resources just like the rest of them. init also doesnt say much about inheriting processes.

As I recall, the theory of it all is that when a process dies, all of its orphaned children are given to the grandparent, who becomes their parent.

As best I can recall, init really really is their parent and it is nonsense to say otherwise. But, I'm wary of altering the text just yet, as the implications of parent/child arrangements revolve around signals (esp. SIGCHLD), and I'm not sure what "init" programs normally do with these inherited daemons. John Vandenberg 03:59, 6 February 2007 (UTC)

[edit] /tmp or /var/tmp as "home" directory?

It's mentioned that daemons ought to use / (root) as home-directory to avoid blocking filesystems (thus preventing them from being unmounted).

However I've read that it's a good idea to use a publically writable directory (usually /tmp or /var/tmp) as home-directory for daemons, so that the daemon has a place to do things like drop core (if it crashes) or (I guess) write files if needed. Of course, if the daemon run as root, it can drop core anywhere, but it's usually a good idea to run them as someone less privliged.

Personally I thought the rationale to avoid blocking filesystems to be a bit wiered, usually daemons runs from boot-up to shut-down, and if you wanted to unmount an important filesystem (e.g. /var with /var/tmp), you'd probably take the system down to single-user and thus killing *all* processes (including daemons) anyway...

Any thoughts?

koppe Tuesday 20 March 2007, 16:25 (CET)

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