nagios plugin to read free disk space in ruby using snmp

disksnmp.rb

#!/usr/bin/ruby
require 'rubygems'
require 'nagios-probe'
require 'snmp'
require 'optparse'

class NagiosDiskCheck < Nagios::Probe
  attr_reader :perfdata
  
  def initialize(opts = {})
    @response = {}
    @perfdata = ""
    @warning_disks = {}
    @critical_disks = {}
    opts[:warn] = 15.0 unless opts[:warn]
    opts[:crit] = 10.0 unless opts[:crit]
    opts[:community] = "public" unless opts[:community]
    raise 'Host not specified' unless opts[:host]
    super(opts)
  end
  
  def run
    mib = SNMP::MIB.new
    mib.load_module "HOST-RESOURCES-TYPES"

    type_fixeddisk = mib.oid "hrStorageFixedDisk"

    SNMP::Manager.open(:Host => @opts[:host], :Community => @opts[:community], :MibModules => ['HOST-RESOURCES-MIB']) do |manager|
      
      manager.walk ["HOST-RESOURCES-MIB::hrFSMountPoint",
                    "HOST-RESOURCES-MIB::hrFSType",
                    "HOST-RESOURCES-MIB::hrFSStorageIndex" ] do | mount_point, type, storage_index |

        (unit, size, used, device_type) = \
          manager.get_value ["HOST-RESOURCES-MIB::hrStorageAllocationUnits.#{storage_index.value}",
                             "HOST-RESOURCES-MIB::hrStorageSize.#{storage_index.value}",
                             "HOST-RESOURCES-MIB::hrStorageUsed.#{storage_index.value}",
                             "HOST-RESOURCES-MIB::hrStorageType.#{storage_index.value}"]
                             
        disk_used = used.to_i * unit.to_i
        disk_size = size.to_i * unit.to_i
        disk_avail = disk_size - disk_used
        disk_pct_used = (disk_used.to_f/disk_size.to_f) * 100
        disk_pct_free = 100 - disk_pct_used
        
        # We only report disks that have size, don't start with "/dev" or "/sys" and are fixed (ie. local) disk
        
        unless disk_size == 0 || mount_point.value.to_s =~ /\/(dev|sys)/ || device_type != type_fixeddisk
          @response[mount_point.value] = {:size => disk_size, :used => disk_used, :available => disk_avail, :percent_used => disk_pct_used, :percent_free => disk_pct_free}
          @perfdata+="#{mount_point.value} (#{disk_used}/#{disk_size}) "
        end
      end
    end
    super  
  end
  
  def check_crit
    @response.each do |disk_name, disk_data|
      if disk_data[:percent_free] < @opts[:crit] then
        @critical_disks[disk_name] = disk_data        
      end
    end
    @critical_disks.size == 0 ? false : true
  end
  
  def check_warn
    @response.each do |disk_name, disk_data| 
      if disk_data[:percent_free] < @opts[:warn] then
        @warning_disks[disk_name] = disk_data
      end
    end
    @warning_disks.size == 0 ? false : true
  end
  
  def crit_message
    "#{@critical_disks.keys.join ', '} below #{@opts[:crit]}% free" 
  end
  
  def warn_message
    "#{@warning_disks.keys.join ', '} below #{@opts[:warn]}% free"
  end
  
  def ok_message
    "All disks above #{@opts[:warn]}% free"
  end
end

options = {}
optparse = OptionParser.new do |opts|
  opts.banner = "Usage: check_disk_snmp [options]"
  
  opts.on("-H", "--host HOST", "Host") do |host|
    options[:host] = host
  end
  
  opts.on("-W", "--warn WARN", Float, "Minimum Disk Warning Limit") do |warn|
    options[:warn] = warn
  end
  
  opts.on("-C", "--crit CRIT", Float, "Minimum Disk Critical Limit") do |crit|
    options[:crit] = crit
  end
  
  opts.on( '-h', '--help', 'Display this screen' ) do
    puts opts
    exit
  end  
end

optparse.parse!
raise OptionParser::MissingArgument if options[:host].nil?


begin
  check = NagiosDiskCheck.new options
  check.run
rescue Exception => e
  puts "Unknown: " + e.message + e.backtrace
  exit Nagios::UNKNOWN
end

puts "#{check.message} | #{check.perfdata}"