Network messaging

Feltis, Ralph C. FELTIRC at
Wed Nov 19 12:47:07 PST 2003

Currently, my use of FreeBSD is limited.  I are using it for network-based
imaging using Frisbee (, great program
btw).  One computer is serving up images using 4.8, and the clients boot
using a customized 4.7 CD.  The clients connect to the server and, depending
on what port they choose, pull down a specific install image.

The clients have to log into FreeBSD, and ideally, would receive a MOTD that
tells them which image is on which port.  Now, I know it's possible to
simply edit the MOTD and create a new CD, but as often as the images change,
it wouldn't be very practical.  That's where my idea of sending some kind of
network data to the server when the client logs on and then the server
replying with the port to image information comes in.  I can't imagine that
I need anything complex, as I am only working in the console with the
clients.  Any ideas?


-----Original Message-----
From: Marty Landman [mailto:MLandman at]
Sent: Wednesday, November 19, 2003 12:24 PM
To: Feltis, Ralph C.; 'freebsd-questions at'
Subject: Re: Network messaging

At 02:51 PM 11/19/2003, Feltis, Ralph C. wrote:
>Is it possible to set some type of simple messaging system between
>FreeBSD machines?  For example, client A pings client B, and then client B
>sends some prespecified text reply to client A.

Ralph, it's certainly possible to setup something a bit more sophisticated 
using ftp and cron to store and routinely check for the presence of a file, 
or in an intranet situation, e.g. if Apache is installed and both boxes 
have http access you could use a CGI script. The details of the 
implementation would/should be based on the detailed need which you haven't 

This raises a question I'm curious about which is in this scenario you 
could easily run into the need for semaphores. I've run into this problem 
running MS-DOS execs on networked windoz boxes (stop that snickering plz) 
and could clearly see the updates stepping on each other's toes.

What is available on fbsd by way of protecting e.g. file writes? FWIW I 
understand the standard flock mechanism I've used with Perl on nix servers 
isn't foolproof, but surely something in the system is....?

Marty Landman   Face 2 Interface Inc 845-679-9387
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