Monitor problems

Ronald Wiemer rwiem at
Tue Oct 7 11:27:02 EDT 1997

For all who have problems running GRASS monitors

There are two versions of the grass-monitor system.

The original version  communicates with the d.* programs by means of 
fifo's, the special files (fifo.1a, fifo.1b etc) you can make with mknod p. 
If something is wrong you can usually kill hanging XDRIVER processes 
(ps -ef | grep x0) and restart GRASS graphics by typing d.mon x0. 

There is another version wich uses message queues for communication
with grass d.* programs. Although the performance of this version is 
much better (when running on Solaris), there are conditions that 
make the complete monitor system hang, making it impossible to start 
new sessions or even stopping the current one.

What you then have to do is kill all XDRIVER processes (see above) 
and remove the message queues. First (as user root) list all message 
queues with:
ipcs -aq
and then you can remove those queues that appear to belong to any 
XDRIVER process:
ipcrm -q QID
where QID has to be replaced by the proper queue ID.
Note that each XDRIVER process has two queues.  
You also need the files fifo.1a, fifo.1b etc. These files are used to 
generate  unique QUEUE KEYS. If your system uses message queues these 
are ordinary files and they contain a text like "don't remove me".  

Ronald Wiemer
R.O.B. / Archis
Kerkstraat 1
NL 3811 CV Amersfoort
The Netherlands

Tel: ++ 31 33 4634233
Fax: ++ 31 33 4653235

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