The variables in the resource group are related only to subagents. The previous example configuration file contains two entries. Each entry represents a subagent and may have the following variables with some value assigned:
registration_file - this field specifies the registration configuration file for each subagent. The Master Agent reads the various entries in this file and creates appropriate entries in its MIB table. The details of this file are explained in "4.3 Agents Registration File". This entry is mandatory for all legacy-type agents. If the value for this variable does not contain a full path, the executable checks the default directory /etc/snmp/conf.
policy - this field has two values: load and spawn. The value load specifies the Master Agent to read this registration entry and create a row entry in its MIB table. If it finds the value spawn, the Master Agent invokes the respective subagent, as stated in the command field of that entry.
command - this is the name of the subagent executable. The command may contain the full path, or if the full path is not mentioned, the executable checks the default directory /usr/lib/bin. The command may use a $PORT macro to provide the port number from which the subagent receives SNMP requests. $PORT is assigned a value by the Master Agent in the registration file of each subagent. The $PORT macro is necessary because the legacy agents or subagents may take different arguments for the port option (such as -p, -n, -port).