If you already have a previous version of the LDM installed and working, then you can probably skip these steps.
Obtain upstream data-feeds
Request authorization at the upstream LDM
Edit the LDM configuration-file, etc/ldmd.conf
Edit the pqact configuration-file, etc/pqact.conf, if appropriate
Edit the scour configuration-file, etc/scour.conf, if appropriate
Edit the LDM user's crontab(1) file
Ensure email forwarding
Ensure that the LDM is started at boot-time
First, find out who your upstream feed site(s) will be. If you don't know and you are qualified to participate in the Unidata IDD, then contact the Unidata Program Center at <idd-connect at unidata.ucar.edu> with the following information:
Ask the administrator of the upstream LDM to add ALLOW entries for your LDM to the upstream LDM's configuration-file, ldmd.conf. For example,
ALLOW UNIDATA your.ldm.host ALLOW NLDN your.ldm.host
This file tells an LDM what to do on startup. Possibilities include executing programs, requesting data, and authorizing connections. The default file that comes with the distribution contains examples. More information on this configuration-file can be found on the ldmd.conf webpage.
Typical entries in this file are:
REQUEST ANY ".*" host1.site1.edu # initially primary-mode REQUEST ANY ".*" host2.site2.edu # initially alternate-mode
For a given feedtype and data-product identifier ERE, you may have more than one such request. You should ensure, however, that the set of data-products referenced by every feedtype/pattern pair is either identical to that of other pairs or completely disjoint from them. So, for example, don't do this
or thisREQUEST UNIDATA ".*" host1.site1.edu REQUEST ANY ".*" host2.site2.edu # overlaps previous
REQUEST IDS|DDPLUS ".*" host1.site1.edu REQUEST IDS|DDPLUS "^SA" host2.site2.edu # overlaps previous
For a given LDM, a trade-off exists between data-product latency and CPU load. This trade-off can be controlled to some extent by the number of REQUEST entries to a given upstream LDM. For more information, see the ldmd.conf webpage.
For more information, see the ldmd.conf webpage.ALLOW ANY-NLDN-WSI-PCWS-NOGAPS \.edu$ ALLOW IDS|DDPLUS \.com$ ^SA ^SAUS
# Exec GEMPAK specific pqact(1) processing EXEC "pqact -f NNEXRAD /usr/local/ldm/etc/GEMPAK/pqact.gempak_nexrad" EXEC "pqact -f ANY-NNEXRAD /local/ldm/etc/GEMPAK/pqact.gempak_decoders"
An EXEC entry for rtstats if the LDM is a member of the Unidata IDD and is a gateway LDM for your institution. LDM statistics are the best way to monitor IDD performance and to identify problems. It is, therefore, crucial that all gateway LDM-s on the IDD report statistics. Also, data on LDM statistics is vital in preparing reports used to obtain funding to support the LDM system.
This file tells the pqact utility how to locally process various classes of data-products. Processing actions include filing the data-product, executing a local program, and piping the data-product to the standard input of a local program. If you're not going to process data-products locally, then you don't need to edit this file.
More information on this configuration-file.
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.
Edit the crontab file of the LDM-user by, for example, executing the command
crontab -eas the LDM-user. Then
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 newlogMore 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 scourThe above runs the scour program to remove too-old files every three hours. You might choose a different time interval.
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:
in the file .forward in the LDM user's home-directory. This file must also be be owned by the LDM user and be world-readable. For security, this file should not be writable by anyone other than the LDM user.user@host
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 LDMHOME=/usr/local/ldm LDMBIN=$LDMHOME/bin LDMADMIN=$LDMBIN/ldmadmin PQCHECK=$LDMBIN/pqcheck PQCAT=$LDMBIN/pqcat PQ=$LDMHOME/data/ldm.pq LOG="logger -p local0.err $0:" case "$1" in start) $LOG 'Starting LDM system...' if [ -x $LDMADMIN ] ; then if su - ldm -c "$LDMADMIN isrunning"; then $LOG "LDM system is already running." else if [ ! -f $PQ ] ; then $LOG "Product-queue doesn't exist. Creating..." if ! su - ldm -c "$LDMADMIN mkqueue"; then $LOG "Aborting..." exit 1 fi else # # Test the product-queue for corruption. # if ! $PQCHECK -l /dev/null -q $PQ; then case $? in 1) $LOG "System error checking product-queue. Aborting..." exit 1 ;; 2) $LOG "Adding writer-counter to product-queue..." if ! $PQCHECK -F -q $PQ; then $LOG "Aborting..." exit 1 fi ;; 3) $LOG "Product-queue was incorrectly closed. " \ "Checking..." if $PQCAT -s -l /dev/null; then $LOG "Product-queue appears OK. " $LOG "Clearing writer-counter..." if ! $PQCHECK -F -q $PQ; then $LOG "Couldn't clear counter. Aborting..." exit 1 fi else $LOG "Product-queue appears corrupt. Deleting." rm $PQ if ! su - ldm -c "$LDMADMIN mkqueue -f"; then $LOG "Couldn't make new product-queue. Aborting..." exit 1 fi fi ;; 4) $LOG "Product-queue is corrupt. Deleting." rm $PQ if ! su - ldm -c "$LDMADMIN mkqueue -f"; then $LOG "Couldn't make new product-queue. Aborting..." exit 1 fi ;; esac fi fi su - ldm -c "$LDMADMIN clean" su - ldm -c "$LDMADMIN start" fi fi ;; stop) $LOG '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
you might wish to use something else (depending on your operating system).
Note that the
-p option is system-dependent.
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.