After struggling for a while on how to get alerts from nagios when the diskspace on a Microsoft Windows server runs low, i decided to write a simple shell script.

Requirements:

• A server running linux with Nagios installed (tested on Ubuntu 10.4.3 LTS with Nagios 3.3.1)
• snmputils installed (the script uses snmpwalk and snmpget)

Code:

#!/bin/sh
# Syntax: check_snmp_diskspace     

# Verify parameters

if [ -z "$5" ]; then
        echo "Syntax: check_snmp_diskspace     "
        echo "Example: check_snmp_diskspace 10.0.0.1 public C: 100 1000"
        exit
fi 

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

SERVER=$1
COMUNITY=$2
VOLUME=$3
CRITLEVEL=$4
WARNLEVEL=$5
exitstatus=$STATE_CRITICAL
# Get logical diskname name of the volume
VOLNUM=`/usr/bin/snmpwalk -c $COMUNITY -v 1 $SERVER .iso.org.dod.internet.mgmt.mib-2.host.hrStorage.hrStorageTable.hrStorageEntry.hrStorageDescr -t 5 | grep $VOLUME | awk '{print $1}' | sed "s/HOST-RESOURCES-MIB::hrStorageDesc..//g" `

# Get the size of the diskspace allready in use
USED=`/usr/bin/snmpget -c $COMUNITY -v 1 $SERVER .iso.org.dod.internet.mgmt.mib-2.host.hrStorage.hrStorageTable.hrStorageEntry.hrStorageUsed.$VOLNUM | awk '{ print $4 }'`

# Get the volume size
SIZE=`/usr/bin/snmpget -c $COMUNITY -v 1 $SERVER .iso.org.dod.internet.mgmt.mib-2.host.hrStorage.hrStorageTable.hrStorageEntry.hrStorageSize.$VOLNUM | awk '{ print $4 }'`

# Get byte value of the volume
VALUE=`/usr/bin/snmpget -c $COMUNITY -v 1 $SERVER .iso.org.dod.internet.mgmt.mib-2.host.hrStorage.hrStorageTable.hrStorageEntry.hrStorageAllocationUnits.$VOLNUM | awk '{ print $4 }'`

# Calculate free disk space
C=$((SIZE-USED))

RESULT=`echo $C*$VALUE/1024/1024 | bc`

#echo "Disk size: $SIZE"
#echo "Disk space used: $USED"
#echo "AllocationUnits: $VALUE"
#echo "Free disk space: $SIZE - $USED = $RESULT MB"

if [ "$RESULT" -le "$CRITLEVEL" ] ; then
        echo "DISKSPACE CRITICAL - "$VOLUME" $RESULT MB"
        exitstats=$STATE_CRITICAL
elif [ "$RESULT" -le "$WARNLEVEL" ] ; then
        echo "DISKSPACE WARNING - "$VOLUME" $RESULT MB"
        exitstatus=$STATE_WARNING
elif [ "$RESULT" -ge "$WARNLEVEL" ] ; then
        echo "DISKSPACE OK - "$VOLUME" $RESULT MB"
        exitstatus=$STATE_OK
else
        echo "DISKSPACE UNKNOWN - "$VOLUME" $RESULT MB"
        exitstatus=$STATE_UNKNOWN
fi

exit $exitstatus

checkcommands.cfg:

define command{
        command_name    check_ntfs_diskspace
        command_line    /usr/local/nagios/libexec/check_ntfs_diskspace $HOSTADDRESS$ public $ARG1$ $ARG2$ $ARG3$
}

service configuration:

define host{
        host_name               server1
        alias                   Example server 1
        address                 the.ip.address
}

define service{
        host_name                       server1
        service_description             DISKSPACE
        check_command                   check_ntfs_diskspace!C:!1000!5000
}