Configuring an LDM Installation

• Unidata Decoders home page

• See the link "Site Configuration for Products" on the GEMPAK homepage .

• See the link "Using LDM-McIDAS Decoders" on the McIDAS decoders webpage.

Workshop-specific instructions.

Edit the scour configuration-file, etc/scour.conf, if appropriate

This file tells the scour utility what old files should be deleted and when to delete them. This is useful if a pqact process is saving data-products as local files; and you want to keep only the most recent files to prevent the file system from becoming full. If you're not doing this, then you probably don't need to edit this file.

More information on this configuration-file.

Workshop-specific instructions.

Edit the LDM-user's crontab(1) file

Edit the crontab file of the LDM-user by, for example, executing the command

crontab -e

• Add an entry to rotate the LDM logfiles by starting a new logfile every day at midnight, changing the names of the old logfiles, and ensuring that the number of logfiles doesn't grow without bound:

  0 0 * * * bin/ldmadmin newlog

  More information on rotating logfiles.

• Add an entry to purge old files if necessary. If you are executing the pqact utility to decode incoming data-products into local files, then add an entry like the following to purge outdated files so that your disk doesn't become full:

  0 1,4,7,10,13,16,19,22 * * * bin/ldmadmin scour

  The above runs the scour program to remove too-old files every three hours. You might choose a different time interval.

Workshop-specific instructions.

Ensure email forwarding

Email for the LDM user can be generated by a crontab(1) entry or by someone trying to contact the LDM administrator at a site. Consequently, you should ensure than any email sent to the LDM user is forwarded to a responsible person. On most UNIX^®-like systems (on which the sendmail(8) daemon is used to deliver email) this is done by having a line like the following:

user@host

Ensure that the LDM is started at boot-time

Although boot-time start-up procedures vary amongst operating systems, each can be tailored to start the LDM. It is best to start the LDM as late as possible in the boot process to avoid interfering with processes that could hang the system (e.g., the syslog daemon). One possible LDM script is:

export PATH=/bin:/usr/bin:/usr/etc:/usr/ucb

LDMHOME=/usr/local/ldm
LDMBIN=$LDMHOME/bin
LDMADMIN=$LDMBIN/ldmadmin
PQCHECK=$LDMBIN/pqcheck
PQCAT=$LDMBIN/pqcat
PQ=$LDMHOME/data/ldm.pq

case "$1" in

start)
    echo 'Starting LDM system...'
    if [ -x $LDMADMIN ] ; then
	if su - ldm -c "$LDMADMIN isrunning"; then
            echo "LDM system is already running."
	else
	    if [ ! -f $PQ ] ; then
		echo "Product-queue doesn't exist.  Creating..."
		if ! su - ldm -c "$LDMADMIN mkqueue"; then
		    echo "Aborting..."
		    exit 1
		fi
	    else
		#
		# Test the product-queue for corruption.
		#
		if ! $PQCHECK -l /dev/null -q $PQ; then
		    case $? in
		    1)  echo "System error checking product-queue.  Aborting..."
			exit 1
			;;
		    2)  echo "Adding writer-counter to product-queue..."
			if ! $PQCHECK -F -q $PQ; then
			    echo "Aborting..."
			    exit 1
			fi
			;;
		    3)  echo "Product-queue was incorrectly closed.  " \
			    "Checking..."
			if $PQCAT -s -l /dev/null; then
			    echo "Product-queue appears OK. "
			    echo "Clearing writer-counter..."
			    if ! $PQCHECK -F -q $PQ; then
				echo "Couldn't clear counter.  Aborting..."
				exit 1
			    fi
			else
			    echo "Product-queue appears corrupt."
			    echo "Renaming with '.bad' suffix and recreating..."
			    mv -f $PQ $PQ.bad
			    if ! su - ldm -c "$LDMADMIN mkqueue"; then
				echo "Couldn't make product-queue.  Aborting..."
				exit 1
			    fi
			fi
			;;
		    4)  echo "Product-queue is corrupt."
			echo "Renaming with '.bad' suffix and recreating..."
			mv -f $PQ $PQ.bad
			if ! su - ldm -c "$LDMADMIN mkqueue"; then
			    echo "Couldn't make product-queue.  Aborting..."
			    exit 1
			fi
			;;
		    esac
		fi
	    fi
	    su - ldm -c "$LDMADMIN clean"
	    su - ldm -c "$LDMADMIN start"
	fi
    fi
    ;;

stop)
    echo 'Stopping the LDM system.'
    if [ -x $LDMADMIN ] ; then
        su - ldm -c "$LDMADMIN stop"
    fi
    ;;

esac

Note that some user-shells do not conform to the the UNIX standard and will not understand the "if ! ..." expressions in the above (e.g., SunOS 5.8's /bin/sh). You can test your user-shell with the following command:

if ! false; then echo OK; fi

Instead of using the echo utility as above, you might wish to use the logger utility in order to write error-messages into the LDM logfile, e.g.,

logger -p local0.err "Couldn't make product-queue.  Aborting..."

Consult the documentation on your operating system or with your system administrator for details on how to incorporate this script (or something similar) into the boot-time start-up procedure of your system.

Workshop-specific instructions.