NET-SNMP-EXTEND-MIB

Description: Allows Net-SNMP agents to execute arbitrary shell commands or scripts and expose their output and exit codes as SNMP OIDs for custom monitoring.

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NET-SNMP-EXTEND-MIB is a widely used extension module for the open-source Net-SNMP agent, allowing an administrator to register arbitrary shell commands or scripts and expose their output, exit codes, and cached results as pollable SNMP objects. It exposes a configuration table listing each registered extension (its token/name, command path, arguments, optional stdin, cache time, execution type, run type, and row storage/status), alongside dynamically generated result objects for each script's output. This is an extremely flexible monitoring mechanism: it is commonly used to expose custom hardware/software status checks not natively covered by other MIBs, such as custom disk health scripts, RAID controller status, application/service process checks, or any locally scripted health check, surfaced through nsExtendOutputTable-style result objects. It depends on the underlying Net-SNMP agent's extend/exec/sh directives and the SNMPv2-SMI/AGENT-CAPABILITIES framework rather than any specific hardware MIB. It is deployed extremely broadly on Linux/Unix servers running the Net-SNMP daemon wherever custom, script-driven monitoring checks are needed alongside standard SNMP data. This is the well-known Net-SNMP extend module, heavily searched by administrators wiring custom shell-script output into SNMP via the extend/nsExtend mechanism.

An administrator would define an entry in nsExtendConfigTable/nsExtendConfigEntry with nsExtendToken naming the check, nsExtendCommand pointing to a health-check script, and nsExtendArgs supplying arguments, then poll the corresponding result object (indexed by that token) to get the script's exit code and output text -- for example a script that checks RAID array status or disk SMART health. nsExtendCacheTime controls how long the cached result is reused before the script reruns, and nsExtendExecType/nsExtendRunType determine whether output is parsed as multiple lines or returned raw. A nonzero exit code surfaced via the extension's result object would indicate the custom health check (e.g., a failed disk or an unhealthy service process) has detected a problem.

Framework for scripted extensions to the Net-SNMP agent, enabling execution of external commands with configurable caching and output.