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[Staging #QHJ-367428]: Real time data for hydrology in Central and South America

Hi Fidel,

> David Andrus has responded positively to the question of making available a 
> *nix
> (Unix/Linux) machine on which your LDM software can be installed.


> His question is:
> "how much space/memory is needed?"

The amount of disk space that will be needed/desired all depends on what data
you want to receive from the IDD and how long of an "archive" you want to
keep.  For sites just getting started with the receipt of real-time data via
the LDM/IDD, we suggest that having access to several hundred gigabytes of
disk space would be appropriate.  The amount of disk space needed for
the LDM installation is small; a couple hundred megabytes is plenty.

As for memory, the answer also depends on how much data one wants to
receive.  Since the LDM queue is memory mapped, one should have enough
free memory for it and all decoding process that one wants to run.  Sites
receiving large volumes of data typically configure the LDM to use 1 or 2 GB
queues, so their systems have to have that much free memory to be able
to run with no disk thrashing.
> Internet connections here at BYU are very good and there should be no problem 
> in
> managing the volume of data from your IDD system with the real time feeds.

Very good.

> My adviser, Dr Jim Nelson, is traveling to 3 countries in Central America in 
> 2 weeks to
> follow up on the project activities that have 2 purposes:
> (a) helping those countries set up their databases in "Hydroserver Light" 
> which is a
>     CUAHSI type of tool. This is part of the World Water Online initiative 
> promoted by
>     Dr Maidment; and
> (b) to develop a flood early warning system (FEWS). And this is where your 
> collaboration
>     is most helpful as the FEWS needs a data stream from real time data and 
> weather
>     forecast.

OK, interesting.

> Please let us know what is the next step, and thank you for your willingness
> to help us.

The sequence of steps now are:

- setup an 'ldm' account on the *nix (Unix/Linux) machine on which the
  LDM will be installed (system administrator)

- register with the Unidata website


- login as 'ldm' on the machine and download the most recent LDM distribution
  to the HOME directory

- follow the instructions for building and installing the LDM:

  Unidata HomePage

    Software -> LDM


   The relevant instructions are found in the links under
   Download, Installation, and Configuration


   The user installing the LDM ('ldm') will need 'root'
   or sudo root capabilities on the system.  Two steps in the
   LDM installation need 'root' privilege: setting up syslog
   logging and changing the mode of two LDM applications to
   have setuid root capabilities.

   The LDM does and should never be run as 'root'; it should
   always be run as a regular user like 'ldm'.  The reason that
   two applications have setuid root privilege is the LDM, by
   default, uses the privileged port 388 (so a process needs
   'root' privilege to get the port), and privilege to send a
   HUP signal to the system logging daemon syslogd/rsyslogd.
   After port 388 access is made, the LDM runs solely as the
   user it was installed as.

Please let us know if you have any questions on how to setup the
LDM.  We routinely help install the LDM on systems for end-users
when they ask for help, so please don't hesitate to ask for
help if desired/needed.


Unidata User Support                                    UCAR Unidata Program
(303) 497-8642                                                 P.O. Box 3000
address@hidden                                   Boulder, CO 80307
Unidata HomePage                       http://www.unidata.ucar.edu

Ticket Details
Ticket ID: QHJ-367428
Department: Support IDD
Priority: Normal
Status: Closed

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