Configure SNMP to work on read-only RPi using tempFilePattern

[David Taylor]

Configure SNMP to work on read-only RPi using tempFilePattern

Raspbian Jessie.

How can I configure SNMP to work with a pass command (shell script) on a
read-only disk? I read that smnp.conf can have a tempFilePattern
specified, but what should I use? Tried /var/log and it doesn't seem to
work (no such instance exists at this OID). The SNMP/pass works
perfectly with a RW file system. Does the Raspberry Pi version of
Jessie even use that variable?

I think the RPi may have been configured with something like the
following. It's the Pi-Star image for use with MMDVM.

https://openenergymonitor.org/forum-archive/node/5331.html

Thanks!
--
David
Web: http://www.satsignal.eu

[David Taylor]

Raspbian Jessie.

How can I configure SNMP to work with a pass command (shell script) on a
read-only disk? I read that smnp.conf can have a tempFilePattern
specified, but what should I use? Tried /var/log and it doesn't seem to
work (no such instance exists at this OID). The SNMP/pass works
perfectly with a RW file system. Does the Raspberry Pi version of
Jessie even use that variable?

I think the RPi may have been configured with something like the
following. It's the Pi-Star image for use with MMDVM.

https://openenergymonitor.org/forum-archive/node/5331.html

Thanks!
--

Cheers,
David
Web: http://www.satsignal.eu

[David Taylor]

[David Taylor]

On 26/11/2017 00:55, Dennis Lee Bieber wrote:
> On Sat, 25 Nov 2017 14:15:00 +0000, David Taylor
> <david-...@blueyonder.co.uk.invalid> declaimed the following:

> That make five times you've posted this message today. If you don't get
> an answer by Monday night (after all, it is a weekend -- and holiday
> weekend for the US -- so may be fewer readers around) then try giving a
> better description.
>
> Based upon https://sourceforge.net/p/net-snmp/patches/319/ I'd assume
> you would still need to provide some location on the file system that is
> RW...
>
> """
> The mkstemp() function generates a unique temporary filename from
> template, creates and opens the file, and returns an open file
> descriptor for the file.
>
> The last six characters of template must be "XXXXXX" and these are
> replaced with a string that makes the filename unique. Since it
> will
> be modified, template must not be a string constant, but should be
> declared as a character array.
>
> The file is created with permissions 0600, that is, read plus write
> for owner only. The returned file descriptor provides both read and
> write access to the file. The file is opened with the open(2)
> O_EXCL
> flag, guaranteeing that the caller is the process that creates the
> file.
> """
Dennis,

Thanks for the reply.

I must apologise for the multiple postings, but each time I posted (a)
Thunderbird said "The newsgroup ... does not exist" or something like
that and (b) reading the newsgroup didn't sho my message. Fixed by
adding an e-mail address to the Server properties. If I can delete the
unanswered messages I would. Doesn't seem to be an option on
Thunderbird. All this because eternal-september appears not to be 100%.

To explain in more detail:

So far:

- doing nothing results in the OID reported as not being present with
the defaults. Supposedly that uses /tmp, and I can create a file in
/tmp even when the disk is read-only, even as a non-priv user.

- I tried adding tempFilePattern to /etc/snmp/snmp.conf, and rebooting,
and it didn't seem to make any difference.

So it's as if either the "tmp" isn't working (which seems unlikely), or
that snmpd isn't using /tmp, or ????

Not sure what they mean by "character array", I guess that's just in the
API call so you can access the file, for snmp.conf you just add the line:

tempFilePattern /tmp/snmpdXXXXXX

Cheers!