Snmpd

SNMP is a standard Internet protocol (RFC 1157) designed for the management and monitoring of network devices. Arch Linux offers Net-SNMP, among other SNMP implementations. This article discusses configuration and testing of the snmpd daemon which is part of the net-snmp package.

Installation

There is a single package for net-snmp in Arch Linux which contains both the snmpd daemon, and the accompanying utilities.

Install the net-snmp package.

Configuration

Note: If /var/net-snmp/snmpd.conf is modified while snmpd is running, any changes will be lost when the daemon is restarted. It is therefore crucial that the snmpd service is stopped while editing the configuration file.

SNMP 1 and 2c

There are three versions of SNMP which are supported by net-snmp: 1, 2c and 3. Versions 1 and 2c start with the same basic configuration, using /etc/snmp/snmpd.conf.

# mkdir /etc/snmp/
# echo rocommunity read_only_community_string >> /etc/snmp/snmpd.conf

The above commands will add a community string that can be used for monitoring. Optionally, you can add another community string used for management. This is not recommended unless you have a specific reason to do so.

# echo rwcommunity read_write_community_string >> /etc/snmp/snmpd.conf

SNMP 3

SNMP v3 adds security and encrypted authentication/communication. It uses a different configuration scheme in /etc/snmp/snmpd.conf and additional configuration in /var/net-snmp/snmpd.conf.

For the former configuration file in /etc/, write directly to it or use the snmpconf wizard:

# mkdir /etc/snmp/
# echo rouser read_only_user >> /etc/snmp/snmpd.conf

$ snmpconf -g basic_setup

For the latter configuration file in /var/, write directly to it or use net-snmp-create-v3-user:

# mkdir -p /var/net-snmp/
# echo createUser read_only_user SHA password1 AES password2 > /var/net-snmp/snmpd.conf

# net-snmp-create-v3-user -ro -a SHA -x AES

Note that once snmpd is (re)started, /var/net-snmp/snmpd.conf will be rewritten, and the clear-text passwords that you have entered will be encrypted.

Daemon

Start/enable snmpd.service.

Testing

If using SNMP 1 or 2c, use one of the following commands to test configuration:

# snmpwalk -v 1 -c read_only_community_string localhost | less
# snmpwalk -v 2c -c read_only_community_string localhost | less

If using SNMP 3, use the following command to test configuration:

# snmpwalk -v 3 -u read_only_user -a SHA -A password1 -x AES -X password2 -l authNoPriv localhost | less

Either way, you should see several lines of data looking something like:

SNMPv2-MIB::sysDescr.0 = STRING: Linux myhost 2.6.37-ARCH #1 SMP PREEMPT Sat Jan 29 20:00:33 CET 2011 x86_64
SNMPv2-MIB::sysObjectID.0 = OID: ccitt.1
DISMAN-EVENT-MIB::sysUpTimeInstance = Timeticks: (307772) 0:51:17.72
SNMPv2-MIB::sysContact.0 = STRING: root@localhost
SNMPv2-MIB::sysName.0 = STRING: myhost
...SNIP...