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python-netsnmpagent Module Copyright (c) 2013 Pieter Hollants <email@example.com> Licensed under the GNU Public License (GPL) version 3 WHAT IS IT? python-netsnmpagent is a Python module that facilitates writing Net-SNMP subagents in Python. Subagents connect to a locally running Master agent (snmpd) over a Unix domain socket (eg. "/var/run/agentx/master") and using the AgentX protocol (RFC2747). They implement custom Management Information Base (MIB) modules that extend the local node's MIB tree. Usually, this requires writing a MIB as well, ie. a text file that specifies the structure, names and data types of the information within the MIB module. python-netsnmpagent was written after a lot of frustration trying to fix the python-agentx module hosted on Sourceforge. I fixed some smaller issues there but when it came to making sure that you could actually walk the whole MIB, not just the variables registered, I realized that it would not make much sense to reimplement the complete behavior of a proper SNMP agent when the NetSNMP API actually can handle those things for you. Also, to be honest, I don't get python-agentx's design :-) python-netsnmpagent, by contrast, in the first line focusses on making the net-snmp C agent API accessible from Python. Though I will try not to just pass through every library call 1:1 but wrap them in a useful manner. net-snmp itself also comes with a Python module (see the "python" subdirectory in the source distribution), however it seems to offer bindings that implement the client side only, not the agent side. REQUIREMENTS python-netsnmpagent requires the net-snmp libraries to be installed, libnetsnmpagent to be precisely. The runtime library is enough, development files are not necessary. DOWNLOAD The PyPI page with distribution archives is available at http://pypi.python.org/pypi/netsnmpagent Binary RPMs for SuSE distributions are available via search.opensuse.org and the Open Build Service Project page at https://build.opensuse.org/package/show?package=python-netsnmpagent&project=home%3Apfhllnts If you wish to follow development more closely clone the GitHub: https://github.com/pief/python-netsnmpagent.git INSTALLATION If you do not use a ready package for your Linux distribution, you can install directly from source using python setup.py install This will most probably require appropriate rights (eg. being "root"). EXAMPLE USAGE There is a well-commented example subagent included, example.py, together with an example MIB, surprisingly named EXAMPLE-MIB.txt. Here's some step-by-step instructions: 1. Make sure net-snmp is installed, snmpd in particular. 2. Run the included "run_example_agent.sh" script. This scripts runs snmpd with a special configuration file on TCP port 5555 and starts the included example agent. 3. From a separate console, run the example SNMP client utilities as written to the screen, eg.: $ snmpwalk -v 2c -c public -M+. localhost EXAMPLE-MIB::exampleMIB EXAMPLE-MIB::exampleUnsigned.0 = Gauge32: 0 EXAMPLE-MIB::exampleUnsignedRO.0 = Gauge32: 0 EXAMPLE-MIB::exampleInteger.0 = INTEGER: 0 EXAMPLE-MIB::exampleIntegerRO.0 = INTEGER: 0 [...] The "-v" option selects version 2c of the SNMP protocol, "-c" specifies the community to use. The special configuration used here uses a read-only community string "public" and a read-write community string "example" (for use with eg. snmpset). The "-M" option modifies the search path for referenced MIBs. Since we reference EXAMPLE-MIB in the specification of the root OID to walk and we have not copied EXAMPLE-MIB.txt to the system's MIBs directory /usr/share/snmp/mibs, we extend (the plus sign "+") the search path with the current directory (which should be the python-netsnmpagent directory). EXAMPLE-MIB::exampleMIB references the root node in the EXAMPLE-MIB. If you haven't looked at the MIB yet, you should probably do so now. If you wish to run the example agent against your system-wide snmpd instance, your /etc/snmp/snmpd.conf (path may vary) should contain lines similar to the following: # Required to allow subagents to connect to snmpd via AgentX protocol master agentx # Required for read-only access from localhost rocommunity public 127.0.0.1 # Required for read-write access from localhost rwcommunity <yoursecret> 127.0.0.1 For SNMP versions 1 and 2c (which are basically those I care about for now), replace "<yoursecret>" with a secret not too obvious, since it is the only protection against unauthorized write access, safe for the localhost access restriction. Because connecting to the system-wide snmpd's AgentX socket requires root rights, start the example agent using sudo: $ sudo python example.py username's password: NET-SNMP version 5.7.1 AgentX subagent connected Serving SNMP requests, press ^C to terminate... API Admittedly the API for writing your own subagents in Python is nowhere next to stable yet. For now, please see the example_agent.py source code for info on how to use the python-netsnmpagent module, but notice that this may change at any time. You might want to follow development on the GitHub repo: https://github.com/pief/python-netsnmpagent.git TODO - stabilize API - unit tests CREDITS python-netsnmpagent was inspired by python-agentx, courtesy of Bozhin Zafirov <firstname.lastname@example.org>. I blatantly ripped some ideas and some lines of code, shame on me. SNMP contexts support and various other additions were implemented by Steven Hiscocks <email@example.com>.