The mini_snmpd configuration is located in /etc/config/mini_snmpd. This configuration is responsible for defining basic snmp attributes, such as location, contact, community and snmp tables for disks and interfaces. This daemon reports only 32bit counters (Counter32).

Configuration consists of single section called mini_snmpd.

The default configuration defines following settings:

config mini_snmpd
        option enabled          '0'
        option ipv6             '0'
        option community        'public'
        option location         ' '
        option contact          ' '
        list disks              '/tmp'
        list disks              '/jffs'
        list interfaces         'lo'
        list interfaces         'br-lan'
        list interfaces         'br-wan' # Max 4

• enabled defines if daemon should be started on by rc script
• ipv6 enables daemon's support of ipv6 sockets - it will listen on :::161 instead of 0.0.0.0:161
• community sets SNMP community string
• location and contact set those base SNMP attributes
• disks and interfaces specifies which filesystems and interfaces should be referenced by corresponding management tables.
• sysName is set automatically from the Hostname on the main System page of the web GUI

Simple example: enable daemon, excluding ipv6 support, defining other parameters.

config mini_snmpd
	option enabled 1
	option ipv6 0
	option community public
	option location ''
	option contact ''
	option disks '/tmp,/jffs'
	option interfaces 'wlan0,br-lan,eth0.1,eth0' # Max 4

Example of the snmpwalk:

$ snmpwalk -m ALL -v 2c -c public 192.168.1.1 
SNMPv2-MIB::sysDescr.0 = STRING: 
SNMPv2-MIB::sysObjectID.0 = OID: SNMPv2-SMI::enterprises
DISMAN-EVENT-MIB::sysUpTimeInstance = Timeticks: (17915) 0:02:59.15
SNMPv2-MIB::sysContact.0 = STRING: 
SNMPv2-MIB::sysName.0 = STRING: OpenWrt
SNMPv2-MIB::sysLocation.0 = STRING: 
RFC1213-MIB::ifNumber.0 = INTEGER: 4
RFC1213-MIB::ifIndex.1 = INTEGER: 1
RFC1213-MIB::ifIndex.2 = INTEGER: 2
RFC1213-MIB::ifIndex.3 = INTEGER: 3
RFC1213-MIB::ifIndex.4 = INTEGER: 4
RFC1213-MIB::ifDescr.1 = STRING: "wlan0"
RFC1213-MIB::ifDescr.2 = STRING: "br-lan"
RFC1213-MIB::ifDescr.3 = STRING: "eth0.1"
RFC1213-MIB::ifDescr.4 = STRING: "eth0"
RFC1213-MIB::ifOperStatus.1 = INTEGER: up(1)
RFC1213-MIB::ifOperStatus.2 = INTEGER: up(1)
RFC1213-MIB::ifOperStatus.3 = INTEGER: up(1)
RFC1213-MIB::ifOperStatus.4 = INTEGER: up(1)
RFC1213-MIB::ifInOctets.1 = Counter32: 19574486
RFC1213-MIB::ifInOctets.2 = Counter32: 18252147
RFC1213-MIB::ifInOctets.3 = Counter32: 124204634
RFC1213-MIB::ifInOctets.4 = Counter32: 126247040
RFC1213-MIB::ifInUcastPkts.1 = Counter32: 91002
RFC1213-MIB::ifInUcastPkts.2 = Counter32: 90354
RFC1213-MIB::ifInUcastPkts.3 = Counter32: 113467
RFC1213-MIB::ifInUcastPkts.4 = Counter32: 113467
RFC1213-MIB::ifInDiscards.1 = Counter32: 0
RFC1213-MIB::ifInDiscards.2 = Counter32: 0
RFC1213-MIB::ifInDiscards.3 = Counter32: 0
RFC1213-MIB::ifInDiscards.4 = Counter32: 0
RFC1213-MIB::ifInErrors.1 = Counter32: 0
RFC1213-MIB::ifInErrors.2 = Counter32: 0
RFC1213-MIB::ifInErrors.3 = Counter32: 0
RFC1213-MIB::ifInErrors.4 = Counter32: 0
RFC1213-MIB::ifOutOctets.1 = Counter32: 127834842
RFC1213-MIB::ifOutOctets.2 = Counter32: 125363371
RFC1213-MIB::ifOutOctets.3 = Counter32: 19332841
RFC1213-MIB::ifOutOctets.4 = Counter32: 20197296
RFC1213-MIB::ifOutUcastPkts.1 = Counter32: 112239
RFC1213-MIB::ifOutUcastPkts.2 = Counter32: 111021
RFC1213-MIB::ifOutUcastPkts.3 = Counter32: 85992
RFC1213-MIB::ifOutUcastPkts.4 = Counter32: 88600
RFC1213-MIB::ifOutDiscards.1 = Counter32: 0
RFC1213-MIB::ifOutDiscards.2 = Counter32: 0
RFC1213-MIB::ifOutDiscards.3 = Counter32: 0
RFC1213-MIB::ifOutDiscards.4 = Counter32: 0
RFC1213-MIB::ifOutErrors.1 = Counter32: 0
RFC1213-MIB::ifOutErrors.2 = Counter32: 0
RFC1213-MIB::ifOutErrors.3 = Counter32: 0
RFC1213-MIB::ifOutErrors.4 = Counter32: 0
HOST-RESOURCES-MIB::hrSystemUptime.0 = Timeticks: (1547471) 4:17:54.71"

As you see walk doesn't catch on disks for some reason.