Category Archives: Linux

Postfix Mail Queue statistics via SNMP

This post documents a small shell script designed to provide basic mail queue statistics via SNMP for Postfix.



The code can be downloaded here.

To install, place the script anywhere in your system and edit it to provide the correct path to the “qshape” perl script that comes with Postfix.

Note: Under openSUSE is part of the postfix-docs package and is not installed by default.

To configure net-snmp, edit your snmpd.conf line and add a line as follows:

pass [oid-of-choice] /bin/ [oid-of-choice]

For example, due to a quirk in a paticular SNMP monitoring package I use, I had to use an OID belonging to Motorola:

pass . /bin/ .

Net-SNMP will return 3 OIDs on query:

.0 :: Incoming
.1 :: Active
.2 :: Deferred


Since the setup of monitoring / statistics tools such as MRTG or RRDTool is site-specific, no provisions are made on this page to provide a complete usage example. A minimal example for RRDTool:
#! /bin/sh
STR="`snmpwalk -OvQ -r 10 -t 5 -v 2c -c publicommunity \
. | perl -ne 's/^/:/;s/\n//;print'`"
rrdtool update /path/to/rr-database.rrd -t incoming:active:deferred N${STR}

This code is free to use and distribute, and the author offers no liability or warranty for it’s misuse.

Limit total bandwidth on Linux

Want to limit the total bandwidth available to a Linux server, and don’t want to do it at the switch or router? Here’s how!

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Making your webserver a little bit more secure.

The most common attack vector on Linux web servers, is to get something uploaded onto the server that can then be executed. Most of these automated attacks try to put their payload into /tmp, which is universally writable by any user, and then execute it.

But what if they couldn’t execute it?

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