Nagios Tips

Nagios Verify
Searching
HostGroup Excludes
Emails with missing hostname
Nagios References
- Thresholds
SNMP
Vendor Refs
- Draytek
- Synology
- Netgear
- APC
  - Mib doesn’t exist
Reading SNMP Mib Files (TBC)

Nagios Verify

nagios4 -v config_file: Reads all data in the configuration files and performs a basic verification/sanity check. Always make sure you verify your config data before (re)starting Nagios.

In my case I use sudo /usr/sbin/nagios4 -v ~/my-nagios-repo/nagios-test.cfg:

It needs to be sudo so it can access everything Nagios can (one day I may try sudo -u nagios CMD)
nagios-test.cfg is the same as my normal nagios.conf except i’ve changed: cfg_dir=./conf.d so it verifies all the changes in my local repo before I push and then pull in /etc/nagios4

More info: Verifying your Nagios Core configuration

Searching

When searching in vscode, try these:

name\s*generic

This will search for name then ignore any whitespace characters (tabs or spaces) then the next bit of text.
eg: use\s*generic-switch

HostGroup Excludes

When applying checks to hostgroups, you can exclude a host.

define service {
  use                   generic-service
  hostgroup_name        windows-machines
  #dauphine is excluded from this check as it is not on the domain.
  host_name             !not-this-host
  service_description   SSH
  check_command
}

Emails with missing hostname

If you have an email alert come through, normally for a service but the hostname seems to be missing, check if the alias definition for the host is blank.

Example:

From: nagios@domain
Sent: Sunday, 12 January 2025 7:23 PM
To: nagiosalerts
Subject: ** PROBLEM Service Alert: /Battery Runtime Remaming is WARNING **

***** Nagios *****

Notification Type: PROBLEM

Service: Battery Runtime Remaming
Host:
Address: 192.168.0.10
State: WARNING

Date/Time: Sun Jan 12 19:22:52 AEDT 2025

define host {
    use                         generic-host
    host_name                   CF-HQUPS3
    alias
    Address                     192.168.0.10
}

Nagios References

Nagios 4.0 Documentation Table of Contents

Nagios Plugin Development Guidelines

Nagios Object Definitions
Nagios Host Definitions
Nagios Service Definitions

Nagios Macro List

https://nagios-plugins.org/doc/man/check_snmp.html
https://nagios-plugins.org/doc/extra-opts.html
https://nagios-plugins.org/development/\

https://www.monitoring-plugins.org/doc/man/index.html
https://www.monitoring-plugins.org/doc/guidelines.html
https://www.monitoring-plugins.org/doc/man/check_http.html

Thresholds

https://www.monitoring-plugins.org/doc/guidelines.html#THRESHOLDFORMAT

# Warning anything between ~ and 35, Critical anything between ~ and 50
!~:35!~:50

# Warning anything between 30~16, critical 15~0
-w 30:16 -c 15:0
!30:16!15:0

SNMP

Ticks

Sometimes timeticks are used in SNMP. To convert to seconds: ticks/100 = seconds

Uptime oids

New: HOST-RESOURCES-MIB::hrSystemUptime (1.3.6.1.2.1.25.1.1.0) - returns timeticks - could be snmp agent / nmc time Old: DISMAN-EVENT-MIB::sysUpTimeInstance (1.3.6.1.2.1.1.3.0) - returns timeticks - could be device time Newer?: 1.3.6.1.6.3.10.2.1.3.0 returns seconds

https://kb.paessler.com/en/topic/61249-why-does-the-snmp-system-uptime-sensor-report-wrong-values

Macros

For the host:

_SNMPCOMMUNITY    public

For the service or check:

$_HOSTSNMPCOMMUNITY$

MIB Installation

CAUTION

I pasted the below to have it handy in the future but you should understand the implications before installing the package, running the program or editing snmp.conf

You can consider using download-mibs

sudo apt-get install snmp-mibs-downloader

It can then be forced or updated with sudo download-mibs

From: https://thejoyofstick.com/blog/2019/05/28/installing-snmp-mib-files-in-linux-ubuntu-12-04-lts/

Either way mibs need to end up in /usr/share/mibs/ or /usr/share/snmp/mibs/ depending on your distribution.

You may also need to consider editing /etc/snmp/snmp.conf to comment out the to comment out the mibs line (apparently)

MIB Formats

This whole section needs fleshing out more.

MIB OID

MIB Downloads

https://mibs.observium.org/ - Haven’t used it but it looks really good

Vendor Refs

Mib doesn’t exist

If you query an APC OID and the response you get is that the MIB doesn’t exist, it may be that the device in query doesn’t support it.

eg: upsAdvTestBatteryProcessStatus which is .1.3.6.1.4.1.318.1.1.1.7.2.14.0 comes back on most APC UPS’s as MIB Doesn’t exist. While it does do this function, it just seems this mib isn’t supported on some models. You can try something like an snmp walk like snmpwalk -v 1 -c public 192.168.1.10 .1.3.6.1.4.1.318.1.1.1.7.2 and see which ones reply.

Reading SNMP Mib Files (TBC)

OID: .1.3.6.1.4.1.318.1.1.1.7.2.3.0

apc                            OBJECT IDENTIFIER ::=  { enterprises 318 }

products                       OBJECT IDENTIFIER ::=  { apc 1 }
~~
hardware                       OBJECT IDENTIFIER ::=  { products 1 }
~~
ups                            OBJECT IDENTIFIER ::=  { hardware 1 }
~~
upsTest                        OBJECT IDENTIFIER ::=  { ups 7 }
~~
upsAdvTest                     OBJECT IDENTIFIER ::=  { upsTest 2 }
~~
upsAdvTestDiagnosticsResults OBJECT-TYPE
   SYNTAX INTEGER {
      ok(1),
      failed(2),
      invalidTest(3),
      testInProgress(4)
   }
   ACCESS read-only
   STATUS mandatory
   DESCRIPTION
      "The results of the last UPS diagnostics test performed."
   ::= { upsAdvTest 3 }