[GEMPAK #RAL-623504]: asking about gempak & crontab (Buenos Aires' university, Argentina)

Hi Gustavo,

After a bit of searching, I found the following comments that Steve Chiswell
made to another user that was having a problem that sounded like the one you
are seeing:

  When you run from cron, you don't have access to your console X server
  (whose magic cookie is unknown to your shell script). 

  To use the hardware GF driver (or the _gf linked program version), you must
  have contact with the X server and your DISPLAY environmental variable must
  be set.

  To generate images from cron, typically most sites will run the Xvfb virtual 
frame
  buffer daemon which allows you to display to a frame buffer in memory, eg:
  /usr/bin/Xvfb :1 -screen 0 1280x1024x24 -shmem 1 &

  This is easiest done at boot time from your init.d. Your DISPLAY variable 
would
  then be your `hostname`:1.

I just checked unidata.at.fcen.uba.ar, and I do not see Xvfb installed, so you
are not running it at boot time:

<as 'ldm' on unidata.at.fcen.uba.ar>
locate Xvfb
 -- not found

So, the recommendation is that you install Xvfb; configure your system to run 
Xvfb
at boot; and then reboot.

I did a quick Google search on how to find which RPM package includes Xvfb, and
I found the recommendation to run:

yum search Xvfb

This worked nicely on your 32-bit, Fedora Core 6 system, and I was able to 
install Xvfb
as follows:

<as 'root'>
[root@UNIDATA ~]# yum search Xvfb
Loading "installonlyn" plugin
Setting up repositories
livna                     100% |=========================| 2.1 kB    00:00     
core                      100% |=========================| 1.1 kB    00:00     
updates                   100% |=========================| 1.2 kB    00:00     
extras                    100% |=========================| 1.1 kB    00:00     
Reading repository metadata in from local files



xorg-x11-server-Xvfb.i386                1.1.1-47.fc6           core            
Matched from:
xorg-x11-server-Xvfb
Xvfb (X Virtual Frame Buffer) is an X server that is able to run on
machines with no display hardware and no physical input devices.
Xvfb simulates a dumb framebuffer using virtual memory.  Xvfb does
not open any devices, but behaves otherwise as an X display.  Xvfb
is normally used for testing servers.



xorg-x11-server-Xvfb.i386                1.1.1-47.10.fc6        updates         
Matched from:
xorg-x11-server-Xvfb
Xvfb (X Virtual Frame Buffer) is an X server that is able to run on
machines with no display hardware and no physical input devices.
Xvfb simulates a dumb framebuffer using virtual memory.  Xvfb does
not open any devices, but behaves otherwise as an X display.  Xvfb
is normally used for testing servers.

I then installed the package using yum:

[root@UNIDATA ~]# yum install xorg-x11-server-Xvfb.i386
Loading "installonlyn" plugin
Setting up Install Process
Setting up repositories
Reading repository metadata in from local files
Parsing package install arguments
Resolving Dependencies
--> Populating transaction set with selected packages. Please wait.
---> Downloading header for xorg-x11-server-Xvfb to pack into transaction set.
xorg-x11-server-Xvfb-1.1. 100% |=========================|  31 kB    00:14     
---> Package xorg-x11-server-Xvfb.i386 0:1.1.1-47.10.fc6 set to be updated
--> Running transaction check

Dependencies Resolved

=============================================================================
 Package                 Arch       Version          Repository        Size 
=============================================================================
Installing:
 xorg-x11-server-Xvfb    i386       1.1.1-47.10.fc6  updates           1.6 M

Transaction Summary
=============================================================================
Install      1 Package(s)         
Update       0 Package(s)         
Remove       0 Package(s)         

Total download size: 1.6 M
Is this ok [y/N]: y
Downloading Packages:
(1/1): xorg-x11-server-Xv 100% |=========================| 1.6 MB    03:32     
Running Transaction Test
Finished Transaction Test
Transaction Test Succeeded
Running Transaction
  Installing: xorg-x11-server-Xvfb         ######################### [1/1] 

Installed: xorg-x11-server-Xvfb.i386 0:1.1.1-47.10.fc6
Complete!

Next, I added running of Xvfb to /etc/rc.d/rc.local:

# Run the virtual frame buffer Xvfb.  This is used to generate
# GEMPAK images from scripts run by cron.

/usr/bin/Xvfb :1 -screen 0 1280x1024x24 -shmem 1 &

I did _not_ reboot the machine because I think that someone should be
there during the reboot in case anything goes wrong.

Please let me know if this helps!

Cheers,

Tom
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Ticket Details
===================
Ticket ID: RAL-623504
Department: Support GEMPAK
Priority: Normal
Status: Closed