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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.

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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

Courtesy of Htkym Creative Commons

Maxwell's_demon.svg Htkym CC, Wikipedia

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

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

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

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.

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    find - the daemon with fins... Commented Apr 16, 2013 at 11:08
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    Oh my God! I'd have never guessed that it was taken from Maxwell's daemon! Commented Apr 16, 2013 at 11:30
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    Sounds like you made an UUOC with ls | cat. You can use the one-line option: ls -1. Commented Apr 16, 2013 at 12:38
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    ld - linker daemon; pwd - print whereabouts daemon; head - hold everything after (so many lines) daemon; find - flatten inscrutable nesting daemon. Commented Apr 16, 2013 at 16:01
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    @TobiasKienzler: Ah. Always thought that was Linus Torvalds evil twin. Also a Fin. Commented Apr 16, 2013 at 18:26
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They're daemons. Simple as that.

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  • instead of "They're", i'd put "Most are" ;) Commented Apr 18, 2013 at 12:47
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    Fair comment @OlivierDulac, but the ones he explicitly listed all actually are. Commented Apr 18, 2013 at 18:04

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