d.mon

[Ken Sibley]

> From: syl at imt.ntou.edu.tw (Shyh-yuan Liu)
> 
> GrassHopper:
> I use grass4.1 in sun4.
> I open the monitor(d.mon start=x3) and not doing.
> use d.mon start=x3 dispaly message fllowing:
> -------------------------------------------------
> Graphics driver [x3] started
> Error - Could not complete locking process for monitor <x3>.
> Lock file is /users/grass4.1/sun4/locks/imtsparc/mon.488045
> Problem selecting x3. Will try once more
> Error - Could not complete locking process for monitor <x3>.
> Lock file is /users/grass4.1/sun4/locks/imtsparc/mon.488045
> ---------------------------------------------------------------
> After I can't close the monitor(d.mon stop=x3) and display the message fllowing:
> "Error - Locking mechanism failed".I have to close the monitor use "kill".
> Can you tell me how to do.
> Thanks in advance.
> 
> 

The first time you start a grass monitor on a particular machine there is
no directory under locks to store the lock file.  Therefore it creates
the directory.  It cannot create the directory and the file in one 
statement so it gives an error because the lock file was not created.
You stop the monitor and the restart it; this time the directory exists
so it creates the lock file just fine.

Another case happens when people reload from a backup tape instead of 
reinstalling.  This often times changes the permissions on the locks
directory which means people cannot create the necessary directories 
under the locks directory, resulting in an error.

Once you have things running you can still get an error message in the
future.  This usually occurs when grass or the display locks up while
running.  You kill the process so the monitor may or may not know 
that things have stopped.  The locks file does not get removed.
You get an error when you try to restart it because the lock file
already exists.  Go in and remove the lock file; with a little looking
you will find the file.  After you have done it once or twice it
becomes second nature.  The same situation happens if openwindows
dies while the monitor is active in grass or if the system blows
up whil the monitor is active in grass.

Hope this helps,
Ken Sibley
USDA-SCS		"Hell, if you understand everything I say,
ksibley at ncg.scs.ag.gov   you'd be me!"  - Miles Davis