Nagios time check using SNMP

When you would like to retrieve the remotely configured time using SNMP and compare it to see how accurate the time is, here is a script to help you out.

This setup does not specifically require NTP to be running on the hosts that are checked, it just requires that the time is correct. Virtual machines for example are advised to have the appropriate "tools" installed to synchronize time. NTP is not desirable for virtual machines.

(Parts of the script are borrowed from http://spielwiese.la-evento.com/xelasblog/archives/27-SNMP-hrSystemDate.0-Datumsformat-anpassen.html)

This is the graph that is created:

The script:

#!/bin/sh

# Nagios plugin to report time difference as received via SNMP compared to the local time.
# Make sure the machine this script runs on (poller/nagios host) is using NTP.

usage() {
# This function is called when a user enters impossible values.
echo "Usage: $0 -H HOSTADDRESS [-C COMMUNITY] [-w WARNING] [-c CRITICAL] [-v VERSION]"
echo
echo " -H HOSTADDRESS"
echo "     The host to check, either IP address or a resolvable hostname."
echo " -C COMMUNITY"
echo "     The SNMP community to use, defaults to public."
echo " -v VERSION"
echo "     The SNMTP version to use, defaults to 2c."
echo " -w WARNING"
echo "     The amount of seconds from where warnings start. Defaults to 60."
echo " -c CRITICAL"
echo "     The amount of seconds from where criticals start. Defaults to 120."
exit 3
}

readargs() {
# This function reads what options and arguments were given on the
# command line.
while [ "$#" -gt 0 ] ; do
  case "$1" in
   -H)
    if [ "$2" ] ; then
     host="$2"
     shift ; shift
    else
     echo "Missing a value for $1."
     echo
     shift
     usage
    fi
   ;;
   -C)
    if [ "$2" ] ; then
     community="$2"
     shift ; shift
    else
     echo "Missing a value for $1."
     echo
     shift
     usage
    fi
   ;;
   -w)
    if [ "$2" ] ; then
     warning="$2"
     shift ; shift
    else
     echo "Missing a value for $1."
     echo
     shift
     usage
    fi
   ;;
   -c)
    if [ "$2" ] ; then
     critical="$2"
     shift ; shift
    else
     echo "Missing a value for $1."
     echo
     shift
     usage
    fi
   ;;
   -v)
    if [ "$2" ] ; then
     version="$2"
     shift ; shift
    else
     echo "Missing a value for $1."
     echo
     shift
     usage
    fi
   ;;
   *)
    echo "Unknown option $1."
    echo
    shift
    usage
   ;;
  esac
done
}

checkvariables() {
# This function checks if all collected input is correct.
if [ ! "$host" ] ; then
  echo "Please specify a hostname or IP address."
  echo
  usage
fi
if [ ! "$community" ] ; then
  # The public community is used when a user did not enter a community.
  community="public"
fi
if [ ! "$version" ] ; then
  # Version 2c is used when a user did not enter a version.
  version="2c"
fi
if [ ! "$critical" ] ; then
  critical="120"
fi
if [ ! "$warning" ] ; then
  warning="60"
fi
}

getandprintresults() {
# This converts the date retreived from snmp to a unix time stamp.
rdatestring=$( snmpget -v $version -c $community $host HOST-RESOURCES-MIB::hrSystemDate.0 | gawk '{print $NF}' )

if [ ! "$rdatestring" ] ; then
  echo "Time difference could not be calculated; no time received."
  exit 3
fi

rdate=$( echo $rdatestring | gawk -F',' '{print $1}' )
rtime=$( echo $rdatestring | gawk -F',' '{print $2}' | gawk -F'.' '{print $1}' )
cldate=$( echo $rdate | gawk -F'-' '{printf("%4i",$1)}; {printf("%02i",$2)}; {printf("%02i",$3)};' )
cltime=$( echo $rtime | gawk -F':' '{printf("%02i",$1)}; {printf("%02i",$2)}; {printf(" %02i",$3)};' )
rdate_s=$( date -d "$cldate $cltime sec" +%s )
ldate_s=$(date +'%s')

# If the calculated difference is negative, make it positive again for comparison.
difference=$(($rdate_s - $ldate_s))
if [ "$difference" -lt 0 ] ; then
  positivedifference=$(($difference*-1))
else
  positivedifference=$difference
fi

if [ "$positivedifference" -gt "$critical" ] ; then
  echo "Time difference is more than $critical seconds: $difference|diff=$difference"
  exit 2
fi

if [ "$positivedifference" -gt "$warning" ] ; then
  echo "Time difference is more than $warning seconds: $difference|diff=$difference"
  exit 1
fi

echo "Time difference is less than $warning seconds: $difference|diff=$difference"
exit 0
}

# The calls to the different functions.
readargs "$@"
checkvariables
getandprintresults

To implement it in Nagios, add these sniplets to nagios.cfg. (or any other applicable nagios file.)

The service for a group.

define service{
        hostgroup_name                  Servertype_Linux
        service_description             time
        _SERVICE_ID                     1856
        use                             SNMP-time
}

The service template.

define service{
        name                            SNMP-time
        service_description             time
        use                             generic-service
        check_command                   check_snmp_time!$_HOSTSNMPCOMMUNITY$!120!60
        max_check_attempts                      30
        normal_check_interval           5
        retry_check_interval            1
        notification_interval           0
        register                                0
}

The command.

define command{
        command_name                    check_snmp_time
        command_line                    $USER1$/check_snmp_time -H $HOSTADDRESS$ -C $ARG1$ -c $ARG2$ -w $ARG3$
}

Comments

Thanks, this is great! Why is

Thanks, this is great!

Why is it not on the Nagios exchange site? http://exchange.nagios.org/directory/Plugins/System-Metrics/Time

Great script doing just what

Great script doing just what I was looking for

Thanks!

Thanks! This is very useful

Thanks! This is very useful to me.

Exactly what i needed. Works

Exactly what i needed. Works great.
Thanks from Brittany, France !

Julien,

It looks like the check

It looks like the check doesn't take differences in timezone into account. The snmpget returns it in the answer string though...

If I come up with a fix, I'll post it here.

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