What is the difference between a daemon and a server process?

Posted on in Categories Howto, Linux, UNIX last updated November 15, 2005

Asked by Pari Kulkarni

Q.What is the difference between a daemon and a server process?

A. A ‘daemon’ is a software process that runs in the background (continuously) and provides the service to client upon request. For example named is a daemon. When requested it will provide DNS service. Other examples are:

  • xinetd (it is a super-daemon, it is responsible for invoking other Internet servers when they are needed)
  • inetd (same as xinetd, but with limited configuration options)
  • sendmail/postfix (to send/route email)
  • Apache/httpd (web server)

Following simple example illustrate relationship between client and daemon.

CLIENT  -> Daemon

Browser Running one daemon for each of the services could significantly increase the load. However if you are running big site (with many user) it is advisable to use dedicated daemon. For example web server or MySQL database server.

A ‘server process’ run runs one time, when called by a daemon. Once done it will stop. For example telnetd (in.telnetd) or ftpd called from xinetd/inetd daemon . By calling server process from daemon you can save the load and memory. Use a server process for small services such as ftpd, telnetd

CLIENT -> Daemon   -> Calls server process
ftp    -> xinetd   -> Calls ftpd
ftp     xinetd stops ftpd

Posted by: Vivek Gite

The author is the creator of nixCraft and a seasoned sysadmin and a trainer for the Linux operating system/Unix shell scripting. He has worked with global clients and in various industries, including IT, education, defense and space research, and the nonprofit sector. Follow him on Twitter, Facebook, Google+.

4 comment

  1. If you have made new chenges in the configuration file you can simply run below:
    # service refresh
    # service reload

    If you want to disable/enable one of the specific service which are under xinetd/inetd daemon you can simply comment out that particular filel in xinetd conf file.

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