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collectd-snmp (5) Linux Manual Page

ByLinux Manual Posted on Updated on

collectd-snmp – Documentation of collectd’s "snmp plugin"

Synopsis

 LoadPlugin snmp
 # ...
 <Plugin snmp>
 <Data "powerplus_voltge_input">
 Type "voltage"
 Table false
 Instance "input_line1"
 Scale 0.1
 Values "SNMPv2-SMI::enterprises.6050.5.4.1.1.2.1"
 </Data>
 <Data "hr_users">
 Type "users"
 Table false
 Instance ""
 Shift -1
 Values "HOST-RESOURCES-MIB::hrSystemNumUsers.0"
 </Data>
 <Data "std_traffic">
 Type "if_octets"
 Table true
 Instance "IF-MIB::ifDescr"
 Values "IF-MIB::ifInOctets" "IF-MIB::ifOutOctets"
 </Data>
 <Host "some.switch.mydomain.org">
 Address "192.168.0.2"
 Version 1
 Community "community_string"
 Collect "std_traffic"
 Interval 120
 </Host>
 <Host "some.server.mydomain.org">
 Address "192.168.0.42"
 Version 2
 Community "another_string"
 Collect "std_traffic" "hr_users"
 </Host>
 <Host "secure.router.mydomain.org">
 Address "192.168.0.7"
 Version 3
 SecurityLevel "authPriv"
 Username "cosmo"
 AuthProtocol "SHA"
 AuthPassphrase "setec_astronomy"
 PrivacyProtocol "AES"
 PrivacyPassphrase "too_many_secrets"
 Collect "std_traffic"
 </Host>
 <Host "some.ups.mydomain.org">
 Address "192.168.0.3"
 Version 1
 Community "more_communities"
 Collect "powerplus_voltge_input"
 Interval 300
 </Host>
 </Plugin>

Description

The "snmp plugin" queries other hosts using SNMP, the simple network management protocol, and translates the value it receives to collectd’s internal format and dispatches them. Depending on the write plugins you have loaded they may be written to disk or submitted to another instance or whatever you configured.

Because querying a host via SNMP may produce a timeout multiple threads are used to query hosts in parallel. Depending on the number of hosts between one and ten threads are used.

Configuration

Since the aim of the "snmp plugin" is to provide a generic interface to SNMP, it’s configuration is not trivial and may take some time.

Since the "Net-SNMP" library is used you can use all the environment variables that are interpreted by that package. See snmpcmd(1) for more details.

There are two types of blocks that can be contained in the "<Plugin snmp>" block: Data and Host:

The Data block

The Data block defines a list of values or a table of values that are to be queried. The following options can be set:

Type type

collectd’s type that is to be used, e. g. “if_octets” for interface traffic or “users” for a user count. The types are read from the TypesDB (see collectd.conf(5)), so you may want to check for which types are defined. See types.db(5) for a description of the format of this file.

Table true|false

Define if this is a single list of values or a table of values. The difference is the following:

When Table is set to false, the OIDs given to Values (see below) are queried using the "GET" SNMP command (see snmpget(1)) and transmitted to collectd. One value list is dispatched and, eventually, one file will be written.

When Table is set to true, the OIDs given to Values (see below) are queried using the "GETNEXT" SNMP command until the subtree is left. After all the lists (think: all columns of the table) have been read several values sets will be dispatches and, eventually, several files will be written. If you configure a Type (see above) which needs more than one data source (for example "if_octets" which needs "rx" and "tx") you will need to specify more than one (two, in the example case) OIDs with the Values option. This has nothing to do with the Table setting.

For example, if you want to query the number of users on a system, you can use "HOST-RESOURCES-MIB::hrSystemNumUsers.0". This is one value and belongs to one value list, therefore Table must be set to false. Please note that, in this case, you have to include the sequence number (zero in this case) in the OID.

Counter example: If you want to query the interface table provided by the "IF-MIB", e. g. the bytes transmitted. There are potentially many interfaces, so you will want to set Table to true. Because the "if_octets" type needs two values, received and transmitted bytes, you need to specify two OIDs in the Values setting, in this case likely "IF-MIB::ifHCInOctets" and "IF-MIB::ifHCOutOctets". But, this is because of the Type setting, not the Table setting.

Since the semantic of Instance and Values depends on this setting you need to set it before setting them. Doing vice verse will result in undefined behavior.

Instance Instance

Sets the type-instance of the values that are dispatched. The meaning of this setting depends on whether Table is set to true or false:

If Table is set to true, Instance is interpreted as an SNMP-prefix that will return a list of values. Those values are then used as the actual type-instance. An example would be the "IF-MIB::ifDescr" subtree. variables(5) from the SNMP distribution describes the format of OIDs.

If Table is set to true and Instance is omitted, then “SUBID” will be used as the instance.

If Table is set to false the actual string configured for Instance is copied into the value-list. In this case Instance may be empty, i. e. "".

InstancePrefix String

If Table is set to true, you may feel the need to add something to the instance of the files. If set, String is prepended to the instance as determined by querying the agent. When Table is set to false this option has no effect.

The "UPS-MIB" is an example where you need this setting: It has voltages of the inlets, outlets and the battery of an UPS. However, it doesn’t provide a descriptive column for these voltages. In this case having 1, 2, … as instances is not enough, because the inlet voltages and outlet voltages may both have the subids 1, 2, … You can use this setting to distinguish between the different voltages.

Values OID [OID …]

Configures the values to be queried from the SNMP host. The meaning slightly changes with the Table setting. variables(5) from the SNMP distribution describes the format of OIDs.

If Table is set to true, each OID must be the prefix of all the values to query, e. g. "IF-MIB::ifInOctets" for all the counters of incoming traffic. This subtree is walked (using "GETNEXT") until a value from outside the subtree is returned.

If Table is set to false, each OID must be the OID of exactly one value, e. g. "IF-MIB::ifInOctets.3" for the third counter of incoming traffic.

Scale Value

The gauge-values returned by the SNMP-agent are multiplied by Value. This is useful when values are transferred as a fixed point real number. For example, thermometers may transfer 243 but actually mean 24.3, so you can specify a scale value of 0.1 to correct this. The default value is, of course, 1.0.

This value is not applied to counter-values.

Shift Value

Value is added to gauge-values returned by the SNMP-agent after they have been multiplied by any Scale value. If, for example, a thermometer returns degrees Kelvin you could specify a shift of 273.15 here to store values in degrees Celsius. The default value is, of course, 0.0.

This value is not applied to counter-values.

Ignore Value [, Value …]

The ignore values allows one to ignore Instances based on their name and the patterns specified by the various values you’ve entered. The match is a glob-type shell matching.

InvertMatch true|false(default)

The invertmatch value should be use in combination of the Ignore option. It changes the behaviour of the Ignore option, from a blacklist behaviour when InvertMatch is set to false, to a whitelist when specified to true.

The Host block

The Host block defines which hosts to query, which SNMP community and version to use and which of the defined Data to query.

The argument passed to the Host block is used as the hostname in the data stored by collectd.

Address IP-Address|Hostname

Set the address to connect to.

Version 1|2|3

Set the SNMP version to use. When giving 2 version "2c" is actually used.

Community Community

Pass Community to the host. (Ignored for SNMPv3).

Username Username

Sets the Username to use for SNMPv3 security.

SecurityLevel authPriv|authNoPriv|noAuthNoPriv

Selects the security level for SNMPv3 security.

Context Context

Sets the Context for SNMPv3 security.

AuthProtocol MD5|SHA

Selects the authentication protocol for SNMPv3 security.

AuthPassphrase Passphrase

Sets the authentication passphrase for SNMPv3 security.

PrivacyProtocol AES|DES

Selects the privacy (encryption) protocol for SNMPv3 security.

PrivacyPassphrase Passphrase

Sets the privacy (encryption) passphrase for SNMPv3 security.

Collect Data [Data …]

Defines which values to collect. Data refers to one of the Data block above. Since the config file is read top-down you need to define the data before using it here.

Interval Seconds

Collect data from this host every Seconds seconds. This option is meant for devices with not much CPU power, e. g. network equipment such as switches, embedded devices, rack monitoring systems and so on. Since the Step of generated RRD files depends on this setting it’s wise to select a reasonable value once and never change it.

See Also

collectd(1), collectd.conf(5), snmpget(1), snmpgetnext(1), variables(5), unix(7)

Authors

Florian Forster <octo [at] collectd.org> Michael Pilat <mike [at] mikepilat.com>

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