[SOLVED] broadcast messages from server to clients

lpallard · 07-06-2010, 10:23 AM

Hi there! I am searching for a way to broadcast a simple message from a server to the other machines (clients) on my local network every day at 22:30 (10:30pm) to warn users that the server will shutdown in 30 minutes (energy saving strategy). Basically, I was thinking to add a cron entry ion the server crontab to do so.

before I go ahead with that, I tried several ways to accomplish this action. I tried the wall command from the server with:

Code:

wall 'message'

but it says Wall: cannto find message (or something like that).

Then I tried simply "wall" and got a text promt to type in my message. At the end I pressed CTRL+D and got a popup displaying my message. So it worked but it was on the server's monitor. How can I send this message to a remote machine? Is wall the proper command to do so?

I also tried using paswordless ssh... It doesnt work. Basically I can login on the remote machine using passwordless ssh but when I issue either kdialog or xmessage, I get error "cannot connect to X server on diaplay 0:0" (or something similar).

I tried also ssh 'wall 'message'' but it also says "cannot connect to X server on diaplay 0:0"

So far I have several ways but nothing really works... There must be a real way to to that??

All machines are Slackware 13.1 based.

T3slider · 07-06-2010, 11:58 AM

I haven't dabbled in this but I remembered this thread which may help you out.

If you can manually (or scriptably) ssh into every box and run through every user on every box you can run

Code:

# XAUTHORITY=/home/user/.Xauthority DISPLAY=:0.0 xmessage "Hi"

as root (assuming /home/user/.Xauthority is used by default for every user), but that will only broadcast to :0.0 and only if that display is being used by user...obviously you could figure out a way to make the above work but it is not ideal and I think it would be better to find an application that can run as a server on each Slackware client and accept messages sent by your server. The linked thread has quite a few possibilities but it is a long read.

onebuck · 07-07-2010, 07:13 PM

Hi

Look at the 'man shutdown' to see the time & warning-message for logged users;

Quote:

excerpt from 'man shutdown';

time When to shutdown.

warning-message Message to send to all users.

The time argument can have different formats. First, it can be an absolute time in the format
hh:mm, in which hh is the hour (1 or 2 digits) and mm is the minute of the hour (in two dig-
its). Second, it can be in the format +m, in which m is the number of minutes to wait. The
word now is an alias for +0.

If shutdown is called with a delay, it creates the advisory file /etc/nologin which causes pro-
grams such as login(1) to not allow new user logins. Shutdown removes this file if it is
stopped before it can signal init (i.e. it is cancelled or something goes wrong). It also
removes it before calling init to change the runlevel.

As for other members then look at woodsman's solution.