Why do some Linux files have a 'd' suffix?

Question

I observed some of the binary files and configuration filenames end with a d. What is reason for putting a d at the end of the file name?

Like httpd, ospfd, pppd, syslogd, telnetd, pptpd, inetd, bootlogd and dhcpd.

Solution 1

They are daemons (Computing) – as in "workers behind the curtain".

http   Daemon - Hypertext Transfer Protocol Daemon
ospf   Daemon - Open Shortest Path First Daemon (89)
ppp    Daemon - Point-to-Point Protocol Daemon
syslog Daemon - Syslog Daemon
telnet Daemon - Telnet server Daemon
pptp   Daemon - Point-to-Point Tunneling Protocol Daemon
dhcp   Daemon - Dynamic Host Configuration Protocol Daemon

All depending on how you interpret the word they can definitively also be demons.

As Wikipedia and Take Our Word For It explains; the words is taken from Maxwell's daemon

_{Maxwell's_demon.svg Htkym CC, Wikipedia}

– "an imaginary agent which helped sort molecules of different speeds and worked tirelessly in the background."

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Else the usage of the word is somewhat in these lines:

daemon: spirit      (polytheistic context)
demon : evil spirit (monotheistic context)

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Fix#1:

And as pointed out by the good Mr. @Michael Kjörling, to emphasize: "Of course, just because the executable's name ends in d doesn't mean it is a daemon."

sed    Stream Editor
dd     Data Description 
chmod  Change file mode bits 
xxd    Hex Dump
find   Find

etc. are examples of frequently used tools ending in d. Then again that would not be an added suffix as in sedd.

ls /usr/bin/*d /bin/*d

Though; typically daemons have the letter d appended at the end.

telnet vs telnetd

Another writeup on the subject of *Nix Daemons.

Solution 2

They're daemons. Simple as that.

Comments

[user]

Of course, just because the executable's name ends in d doesn't mean it is a daemon. See ls /usr/bin/*d for examples.

[Tobias Kienzler]

find - the daemon with fins...

[goldilocks]

Also: Disk And Execution MONitor.

[Bakuriu]

Oh my God! I'd have never guessed that it was taken from Maxwell's daemon!

[Kaz]

ld - linker daemon; pwd - print whereabouts daemon; head - hold everything after (so many lines) daemon; find - flatten inscrutable nesting daemon.

[Runium]

@TobiasKienzler: Ah. Always thought that was Linus Torvalds evil twin. Also a Fin.

[Tobias Kienzler]

@Sukminder :-D That's what that daemonic dolphin wanted you to believe

[Runium]

@TobiasKienzler: lol, This actually is starting to mold into some fine ideas for a good geek short story.

[Tobias Kienzler]

Oh god, what have I done? Wait, what letter did that deity end with?!

[Admin]

id - I daemon.

[Simon Gates]

Linguistically, daemons and demons are the same thing and renderings of the same word. ‘Dæmon’ is the Greek word for a minor deity. After christianity started using Greek, the word got repurposed to mean evil pagan deities, and then just lost all non-negative connotations and eventually got simplified to demon. It's still the same word in German, though: Dämon (Daemon).

[Olivier Dulac]

instead of "They're", i'd put "Most are" ;)

[tink]

Fair comment @OlivierDulac, but the ones he explicitly listed all actually are.