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snmpd - "simple and extendable SNMP daemon"


Variable Assignments
Section Separators
Include Directives
Mib Variable Assignments
See Also


snmpd [-dh] [-c file] [-D options] [-I paths] [-l prefix] [-m variable [= value]] [-p file]


The snmpd daemon servers the internet SNMP (Simple Network Managment Protocol). It is intended to serve only the absolute basic MIBs and implement all other MIBs through loadable modules. In this way the snmpd can be used in unexpected ways.

The options are as follows:

-d This option is used for debugging snmpd and causes it not to daemonize itself.
-h This option prints a short usage message.
-c file Use file as configuration file instead of the standard one.
-D options Debugging options are specified with a -o flag followed by a comma separated string of options. The following options are available.
dump This option causes all sent and received PDUs to be dumped to the terminal.
events This causes the debugging level of the event library (see eventlib(3)) to be set to 10.
trace = level This option causes the snmp library trace flag to be set to the specified value. The value can be specified in the usual C-syntax for numbers.
-I paths This option specifies a colon separated list of directories to search for configuration include files. The default is /etc:/usr/etc/:/usr/local/etc. These paths are only searched for include specified within <> parentheses.
-l prefix The prefix is used as the default basename for the pid and the configuration files.
-m variable [= value] Define a configuration variable.
-p file Specify an alternate pid file instead of the default one.


The snmpd reads its configuration from either the default or the user specified configuration file. The configuration file consists of the following types of lines:
  • variable assignments
  • section separators
  • include directives
  • MIB variable assignments

If a line is too long it can be continued on the next line by ending it with a backslash. Empty lines and lines in which the first non-blank character is a "#" sign are ignored.

All MIB variable assignments of the entire configuration (including nested configuration files) are handled as one transaction, i.e. as if they arrived in a single SET PDU. Any failure during the initial configuration read causes snmpd to exit. A failure during the configuration read caused by a module load causes the loading of the module to fail.

The configuration is read during initialisation of snmpd, when a module is loaded and when snmpd receives a SIGHUP.


Variable assignments can take one of two forms:
variable := string
variable ?= string

The string reaches from the first non-blank character after the equal sign until the first new line or "#" character. In the first case the string is assigned to the variable unconditionally, in the second case the variable is only assigned if it does not exist yet.

Variable names must begin with a letter or underscore and contain only letters, digits or underscores.


The configuration consists of named sections. The MIB variable assignments in the section named "snmpd" are executed only during initial setup or when snmpd receives a SIGHUP. All other sections are executed when either a module with the same name as the section is loaded or snmpd receives a SIGHUP and that module is already loaded. The default section at the start of the configuration is "snmpd". One can switch to another section with the syntax

Where secname is the name of the section. The same secname can be used in more than one place in the configuration. All of these parts are collected into one section.


Another configuration file can be included into the current one with the include directive that takes one of two forms:
.include "file"
.include <"file">

The first form causes the file to be searched in the current directory, the second form causes the file to be searched in the directories specified in the system include path. Nesting depth is only restricted by available memory.


A MIB variable is assigned with the syntax
oid [ suboids ] = value

oid is the name of the variable to be set. Only the last component of the entire name is used here. If the variable is a scalar, the index (.0) is automatically appended and need not to be specified. If the variable is a table column, the index (suboids) must be specified. The index consist of elements each seperated from the previous one by a dot. Elements may be either numbers, strings or hostnames enclosed in [] brackets. If the element is a number it is appended to the current oid. If the element is a string, its length and the ASCII code of each of its characters are appended to the current oid. If the element is a hostname, the IP address of the host is looked up and the four elements of the IP address are appended to the oid.

For example a oid of

results in the oid

The value of the assignment may be either empty, a string or a number. If a string starts with a letter or an underscore and consists only of letters, digits, underscores and minus signs, it can be written without quotes. In all other cases the string must be enclosed in double quotes.


A variable substitution is written as

where variable is the name of the variable to substitute. Using an undefined variable is considered an error.


/etc/<prefix.config> Default configuration file, where the default <prefix> is "snmpd".
/var/run/<prefix.pid> Default pid file.
/etc:/usr/etc/:/usr/local/etc This is the default search path for system include files.
The definitions for the MIBs implemented in the daemon.






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