First off, you need to write a mib module first before you can do this part of the tutorial. We assume you have read and completed the mib module portion of the toolkit tutorial. This part of the tutorial shows how to install a dynamic module into the agent, assuming you already have written a mib-module which we'll then compile into a dynamic module. For example purposes, we'll refer to some example MIB objects and code: the NET-SNMP-TUTORIAL-MIB MIB, and the example mib module and it's header file.
Note: For this to work, you must have compiled the net-snmp package with dynamicly loadable module support turned on, as well as built it with --enable-shared turned on. (It's on by default, if your system supports it). You can check for support in your agent but looking at the output of the "snmpd -H" command for the "dlmod" token. If its listed, the compiled agent supports it.
Note: All command line options below assume you have an appropriately setup ~/.snmp/snmp.conf file that allows you to not have to specify a snmp version number, community name, username, or whatever else in order to talk to your agent. The agent, of course, must have a matching /usr/local/share/snmp/snmpd.conf file (or equivalent).
Here are the files discussed in this example so you can download them:
|Makefile||A simple makefile used to build the projects|
|NET-SNMP-TUTORIAL-MIB.txt||The MIB we'll be writing code for|
|nstAgentPluginObject.h||The mib module's header file|
|nstAgentPluginObject.c||The mib module's C source code|
The shared object loader calls the "init_nstAgentPluginObject()" function in the above code when it gets loaded, and calls the "deinit_nstAgentPluginObject()" when (and if) the module is unloaded. These function names to use are built by adding the shared object's module name (UCD-DLMOD-MIB::dlmodName) to the `init_' and `deinit_' prefixes.
Steps to build the shared object:
Steps to test the shared object:
nstAgentPluginObject.0 = No Such Object available on this agent at this OID
dlmodStatus.1 = create(6)
SNMP table: dlmodTable dlmodName dlmodPath dlmodError dlmodStatus unloaded
dlmodName.1 = "nstAgentPluginObject" dlmodName.1 = "/path/to/nstAgentPluginObject.so"
SNMP table: dlmodTable dlmodName dlmodPath dlmodError dlmodStatus nstAgentPluginObject /path/to/nstAgentPluginObject.so unloaded
dlmodStatus.1 = loaded(1)
SNMP table: dlmodTable dlmodName dlmodPath dlmodError dlmodStatus nstAgentPluginObject /path/to/nstAgentPluginObject.so loaded
nstAgentPluginObject.0 = INTEGER: 3
You can also load shared objects using the "dlmod" token in the snmpd.conf file by putting a line like this in your snmpd.conf file:
dlmod nstAgentPluginObject /path/to/nstAgentPluginObject.so
The first argument specifies the shared object's module name
(UCD-DLMOD-MIB::dlmodName) and second argument specifies the
full pathname of the shared object file.
Last modified: Thursday, 26-May-2011 23:21:32 UTC
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