[ale] SNMP oid for file descriptors

[Alex Carver]

I use this approach to get the temperatures of my Raspberry Pi
processors remotely.

My snmpd.conf file contains this line:
extend     temp    /usr/local/bin/snmp_temperature.sh

The shell script it points to is just this:

#!/bin/bash
/bin/sed 's:\([0-9]\{2\}\)\([0-9]\{3\}\):\1.\2:'
/sys/class/thermal/thermal_zone0/temp

If I walk the tree I get this:

$ snmpwalk -v 2c -c secret localhost .1.3.6.1.4.1.8072.1.3
iso.3.6.1.4.1.8072.1.3.2.1.0 = INTEGER: 1
iso.3.6.1.4.1.8072.1.3.2.2.1.2.4.116.101.109.112 = STRING:
"/usr/local/bin/snmp_temperature.sh"
iso.3.6.1.4.1.8072.1.3.2.2.1.3.4.116.101.109.112 = ""
iso.3.6.1.4.1.8072.1.3.2.2.1.4.4.116.101.109.112 = ""
iso.3.6.1.4.1.8072.1.3.2.2.1.5.4.116.101.109.112 = INTEGER: 5
iso.3.6.1.4.1.8072.1.3.2.2.1.6.4.116.101.109.112 = INTEGER: 1
iso.3.6.1.4.1.8072.1.3.2.2.1.7.4.116.101.109.112 = INTEGER: 1
iso.3.6.1.4.1.8072.1.3.2.2.1.20.4.116.101.109.112 = INTEGER: 4
iso.3.6.1.4.1.8072.1.3.2.2.1.21.4.116.101.109.112 = INTEGER: 1
iso.3.6.1.4.1.8072.1.3.2.3.1.1.4.116.101.109.112 = STRING: "54.230"
iso.3.6.1.4.1.8072.1.3.2.3.1.2.4.116.101.109.112 = STRING: "54.230"
iso.3.6.1.4.1.8072.1.3.2.3.1.3.4.116.101.109.112 = INTEGER: 1
iso.3.6.1.4.1.8072.1.3.2.3.1.4.4.116.101.109.112 = INTEGER: 0
iso.3.6.1.4.1.8072.1.3.2.4.1.2.4.116.101.109.112.1 = STRING: "54.230"



The last four OIDs of 116.101.109.112 translates to "temp" as appears in
the extend configuration.  The '4' before that I believe marks the
boundary of the offical OID tree (for which the values before it are
documented) and the user defined OID values (the "temp" in this case")

There's also a pass through method that requires a bit more effort on
the scripting side but provides a bit more flexibility.

On 2018-08-10 11:20, Todor Fassl wrote:> Ah, now I am starting to get it.
> 
> It occurs to me that this is a good approach in general for solving all
> kinds of system monitoring problems. Like I once worked for a web
> hosting service. We stored info about each account in a file within the
> account. But how to get to that info remotely? We considered picking a
> port number, inventing our own protocol, and writing a TCP/IP server.
> Should have just added it to snmp and used snmp's own security protocols
> to protect it. Before that I worked for a company that wrote drivers for
> medical scanners. We *did* pick a port number and invent our own
> protocol to get status info from the scanner.
> 
> The beauty of the thing, besides not re-inventing the wheel, is that
> standard tools like nagios could be used to monitor the data.
> 
> I'll have to do some research.
> 
> 
> 
> On 08/07/2018 10:55 AM, Alex Carver via Ale wrote:
>> You create your own OID table entry.  Use the extend or pass-through
>> capability of snmpd and a shell script to generate an SNMP table or tree
>> output and then obtain it starting with the base tree
>>
>> NET-SNMP-EXTEND-MIB::nsExtensions (.1.3.6.1.4.1.8072.1.3)
>>
>>
>>
>> On 2018-08-07 07:00, Todor Fassl via Ale wrote:
>>> Well, I am not too worried about being able to calculate it. What I
>>> cannot figure out is how to get to the numbers remotely.
>>>
>>>
>>> On 08/06/2018 01:21 PM, Jerald Sheets wrote:
>>>> Why not pull the number of file handles you have: "sysctl fs.file-nr"
>>>> and compare it to current open file handles “lost |wc -l” and do a
>>>> multi-graph for the metrics.  Then, also subtract the two and alert
>>>> when you get below whatever threshold you want?
>>>>
>>>> I think you should be able to knock that out in BASH or Perl.
>>>>
>>>> —j
>>>>
>>>>
>>>>
>>>>> On Aug 6, 2018, at 1:49 PM, Todor Fassl via Ale <ale at ale.org> wrote:
>>>>>
>>>>> Ultimately, what I want to do is to configure nagios to alert me when
>>>>> a server is getting low on file handles. There are a couple of
>>>>> scripts on the nagios web site but they look kind of hokey.
>>>>>
>>>>> I think all I should have to do is cut/pasete the right SNMP object
>>>>> identifier into the nagios snmp plugin. But how to find that oid?
>>>>>
>>>>>
>>>>> _______________________________________________
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>>>
>>
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>