Problem with graph monitor when many grass users on one computer

Ken Sibley ksibley at
Thu Mar 17 09:17:01 EST 1994

> I have recently installed Grass4.1 on a Convex C3220.
> Everything seems to work fine, except that the graphic
> monitors get hung when I run whole labgroups with 
> 10-13 X-terminals.
> I tried to duplicate the XDRIVER and attach only up to 4 
> monitors to each copy of the driver, but unsuccessful.
> Is there anybody who has experience in running simultaneous
> ten grass sessions from one computer?
> All suggestions are welcome.
> _________________________________________________________________
> Hans Hauska				e-mail: hans at
> Div of geoinformatics 			voice: +46-8-790 7341
> Dept of geodesy and photogrammetry      fax:   +46-8-790 6610
> Royal Inst of Technology
> S-100 44 STOCKHOLM
> Sweden
> _________________________________________________________________

We have run 9 seessions at once when teaching classes.  Our platform is
a Sun machine, but maybe one of the problems we had is the same as yours.
It does not matter how many seperate XDRIVER binaries you have as each 
call spawns a new process.  You will need to have a seperate monitor
listed in the monitorcap file, with each monitor definition having 
seperate fifos.  No two users can use the same monitor at the same
time.  They can check which one's are being used with the d.mon -L
command.  If this is ok then there is one other thing we ran into.
In the kernel there is a fifo count parameter.  Any time we ran over
seven monitors, each monitor using two fifos, our monitors died.  We
had to modify that parameter and regen the kernel.  

Hope this helps,
Ken Sibley
ksibley at

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