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[LDM #ADA-874007]: This is driving me nuts!



Hi Gilbert and Steve,

Here is a bit more information on the EXEC problem that Gilbert is
experiencing on weather3.admin.niu.edu:

I modified /usr/local/bin/make_index to:

- not modify PATH

  This was done because of a recommendation I read in:

  
http://askubuntu.com/questions/604406/g-error-trying-to-exec-as-execvp-no-such-file-or-directory

  "You should not overwrite $PATH in your script."

- echo the PATH in-scope to a log file for review


Here is the value of PATH that the script is seeing on weather3:

/home/ldm/ldm-6.12.14/bin:/usr/bin:/bin

Here is the PATH in the environment in which the LDM is started:

/usr/local/bin:/usr/local/bin/wxp6:/bin:/usr/bin:/usr/games:/usr/lib/mh:/usr/bin/mh:/home/ldm/bin:/home/ldm/wxpscripts:/home/ldm/decoders:/home/ldm/decoders/bin:/home/ldm/wxpscripts:/home/ldm:/usr/lib64:/lib64:/usr/lib:/sbin:/usr/sbin:.:/home/gempak/NAWIPS/os/linux64/bin:/home/gempak/NAWIPS/bin:/home/gempak/NAWIPS/os/linux64/bin


For comparison, here is the same information on weather.admin.niu.edu:

PATH in-scope in /usr/local/bin/make_index:

/home/ldm/ldm-6.12.14/bin:/usr/local/bin:/bin:/usr/bin:/usr/games:/usr/lib/mh:/usr/bin/mh:/home/ldm/bin:/home/ldm/wxpscripts:/home/ldm/gempakscripts:/home/ldm/decoders:/home/ldm/decoders/bin:/home/ldm/util:/usr/local/etc:/usr/lib64:/sbin:/usr/sbin:.

PATH in environment in which the LDM is started:

/usr/local/bin:/bin:/usr/bin:/usr/games:/usr/lib/mh:/usr/bin/mh:/home/ldm/bin:/home/ldm/wxpscripts:/home/ldm/gempakscripts:/home/ldm/decoders:/home/ldm/decoders/bin:/home/ldm/util:/usr/local/etc:/usr/lib64:/sbin:/usr/sbin:.

Comment:

- apparently, PATH is being modified on weather3 in a different way than
  on weather

  The only candidate for modifying PATH is 'ldmadmin', and since this code is
  the same on weather and weather3, the likely culprit is 'perl' 
(/usr/bin/perl).
  I say this because of the code in 'ldmadmin' that modifies the PATH to put
  the LDM bin directory first:

# Ensure that the utilities of this version are favored
$ENV{'PATH'} = "$ldmhome/ldm-6.12.14/bin:$ENV{'PATH'}";

  As a test, I commented out this PATH twiddling in 'ldmamdin' on weather3 and
  removed the fully qualified invocation of 'make_index' in ~ldm/etc/pqact.conf.
  After restarting the LDM, the EXEC problem disappeared:

  PATH in-scope in 'make_index' with PATH twiddling in 'ldmadmin':

/home/ldm/ldm-6.12.14/bin:/usr/bin:/bin

  PATH in-scope in 'make_index' after removal of PATH twiddling in 'ldmadmin':

/usr/local/bin:/usr/local/bin/wxp6:/bin:/usr/bin:/usr/games:/usr/lib/mh:/usr/bin/mh:/home/ldm/bin:/home/ldm/wxpscripts:/home/ldm/decoders:/home/ldm/decoders/bin:/home/ldm/wxpscripts:/home/ldm:/usr/lib64:/lib64:/usr/lib:/sbin:/usr/sbin:.:/home/gempak/NAWIPS/os/linux64/bin:/home/gempak/NAWIPS/bin:/home/gempak/NAWIPS/os/linux64/bin

Tentative Conclusion:

- Perl is incorrectly changing the PATH in 'ldmadmin' on weather3

  What may this be?

  I think that the likely answer is that the length of PATH in the environment
  in which the LDM is started on weather3 is too long for Perl. I am now 
Googling
  to see if anyone has reported this kind of problem anywhere else.

Solution?

- the easiest thing to do would be to trim down the PATH on weather3 so that it
  is about the same length of PATH on weather (the PATH for 'ldm' on weather is
  measurably shorter than it is on weather3)

  If this test is made, the mod I made to ~ldm/bin/ldmadmin will need to be
  undone to see the effect.

More later...


Cheers,

Tom
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Ticket Details
===================
Ticket ID: ADA-874007
Department: Support LDM
Priority: Normal
Status: Open


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