Windows – Use Nagios(or alternative free product) to monitor uptime of 50+ remote machines with dynamic IP addresses

i found a plugin for this (can't remember where), which seems to work well in production.

define command{
    command_name    check_numfiles
    command_line    $USER1$/check_numoffiles.sh $ARG1$
    }

and

check_command           check_numfiles!-d /var/spool/sms/failed -w 1 -c 2

it goes warning if the directory contains one or more files, critical if two or more. the plugin uses find, so modifying it with a -mtime xxx to check only for files over a certain age would be trivial.

the plugin itself is:

#!/bin/sh
#
# ## Plugin for Nagios to monitor how man files a directory contain
# ## Written by Bernd Mueller (http://www.lisega.de/)
# ##
# ## - 20070426 coded and tested for Linux
# ## - no jet published on NagiosExchange
#
#
# ## You are free to use this script under the terms of the Gnu Public License.
# ## No guarantee - use at your own risc.
#
#
# Usage: ./check_nomoffiles -d <path> -w <warn> -c <crit>
#
# ## Description:
#
# This plugin determines the number of files in a directory
# and compares it with the supplied thresholds.
#
# ## Output: 
#
# The plugin prints the Count of Files in the directory followed by "ok" or
# either "warning" or "critical" if the corresponing threshold is reached.
#
# Exit Codes
# 0 OK       Directory Count of files checked and everything is ok
# 1 Warning  Directory Count of files above "warning" threshold
# 2 Critical Directory Count of files above "critical" threshold
# 3 Unknown  Invalid command line arguments or could not determine directory size
#
# Example: check_numoffiles -d . -w 1000 -c 1400
#
# 121 Files - ok         (exit code 0)
# 1234 Files - warning   (exit code 1)
# 1633 Files - critical  (exit code 2)


# Paths to commands used in this script.  These
# may have to be modified to match your system setup.

PATH=""

find="/usr/bin/find"
xargs="/usr/bin/xargs"
tail="/usr/bin/tail"
awk="/usr/bin/awk"
cut="/usr/bin/cut"
wc="/usr/bin/wc"

PROGNAME=`/bin/basename $0`
PROGPATH=`echo $0 | /bin/sed -e 's,[\\/][^\\/][^\\/]*$,,'`
REVISION="Revision 1.0"
AUTHOR="(c) 2007 Bernd Mueller (http://www.lisega.de/)"

# Exit codes
STATE_OK=0
STATE_WARNING=1
STATE_CRITICAL=2
STATE_UNKNOWN=3
STATE_DEPENDENT=4

print_revision() {
    echo "$REVISION $AUTHOR"
}

print_usage() {
    echo "Usage: $PROGNAME -d <path> -w <warn> -c <crit>"
    echo "Usage: $PROGNAME --help"
    echo "Usage: $PROGNAME --version"
}

print_help() {
    print_revision $PROGNAME $REVISION
    echo ""
    echo "Directory Files monitor plugin for Nagios"
    echo ""
    print_usage
    echo ""
}

# Make sure the correct number of command line
# arguments have been supplied

if [ $# -lt 1 ]; then
    print_usage
    exit $STATE_UNKNOWN
fi

# Grab the command line arguments

thresh_warn=""
thresh_crit=""
exitstatus=$STATE_WARNING #default
while test -n "$1"; do
    case "$1" in
        --help)
            print_help
            exit $STATE_OK
            ;;
        -h)
            print_help
            exit $STATE_OK
            ;;
        --version)
            print_revision $PROGNAME $VERSION
            exit $STATE_OK
            ;;
        -V)
            print_revision $PROGNAME $VERSION
            exit $STATE_OK
            ;;
        --dirname)
            dirpath=$2
            shift
            ;;
        -d)
            dirpath=$2
            shift
            ;;
        --warning)
            thresh_warn=$2
            shift
            ;;
        -w)
            thresh_warn=$2
            shift
            ;;
        --critical)
            thresh_crit=$2
            shift
            ;;
        -c)
            thresh_crit=$2
            shift
            ;;
        *)
            echo "Unknown argument: $1"
            print_usage
            exit $STATE_UNKNOWN
            ;;
    esac
    shift
done

##### Get size of specified directory

error=""
statresult=`$find $dirpath -maxdepth 1 -type f | $wc -l |$tail -1`
dirsize=`echo $statresult`
result="ok"
exitstatus=$STATE_OK

##### Compare with thresholds

if [ "$thresh_warn" != "" ]; then
    if [ $dirsize -ge $thresh_warn ]; then
        result="warning"
        exitstatus=$STATE_WARNING
    fi
fi
if [ "$thresh_crit" != "" ]; then
    if [ $dirsize -ge $thresh_crit ]; then
        result="critical"
        exitstatus=$STATE_CRITICAL
    fi
fi

echo "$dirsize Files - $result"
exit $exitstatus

I see one specific problem: your allowed_hosts in your nrpe.conf (on the client) should be set to the nagios monitor master host IP number. Setting this to local host means that your client and the monitor master are the same host (i.e. local) which is unlikely.

Another situation, sometimes remote plugins do not have encyption enabled, so when nagios issues the command connection to the remote npre fails. You can try checking nrpe with and without SSL encoding through a -n switch to check_nrpe.

In any event use the command, /usr/lib/nagios/plugins/check_nrpe and check the remote host nrpe from the nagios monitor master server. You get a lot of information that way.

EX: /usr/lib/nagios/plugins/check_nrpe -H HOSTNAME

If nrpe is not running on the monitored host, then you're not going to get anything back.