I am new to Linux. 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.
Why do some Linux files have a 'd' suffix?
filenames;terminology
They are daemons (Computing)  as in workers behind the curtain.http   Daemon - Hypertext Transfer Protocol Daemonospf   Daemon - Open Shortest Path First Daemon (89)ppp    Daemon - Point-to-Point Protocol Daemonsyslog Daemon - Syslog Daemontelnet Daemon - Telnet server Daemonpptp   Daemon - Point-to-Point Tunneling Protocol Daemondhcp   Daemon - Dynamic Host Configuration Protocol DaemonAll depending on how you interpret the word they can definitively also bedemons.As Wikipedia and Take Our Word For It explains; the words is taken from Maxwell's daemonMaxwell'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 Kjrling, to emphasize: Of course, just because the executable's name ends in d doesn't mean it is a daemon. sed    Stream Editordd     Data Description chmod  Change file mode bits xxd    Hex Dumpfind   Findetc. are examples of frequently used  tools ending in d. Then again that wouldnot be an added suffix as in sedd.ls /usr/bin/*d /bin/*dThough; typically daemons have the letter d appended at the end.telnet vs telnetdAnother writeup on the subject of *Nix Daemons.