SNMP is a tool designed for the management and monitoring of network devices. The Net-SNMP package is one implementation of SNMP that is available for Arch Linux. This article discusses the configuration and testing of the snmpd daemon that ships with Arch's net-snmp package.
There is one package for net-snmp in Arch Linux which contains both the snmpd daemon, and the accompanying utilities.
# pacman -S net-snmp
Note that it is crucial that the snmpd service is not running while editing configuration files for it, especially /var/net-snmp/snmpd.conf.
Add the daemon to /etc/rc.conf:
DAEMONS=(syslog-ng network netfs crond httpd snmpd)
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 -p /etc/snmp/ # echo rocommunity read_only_user >> /etc/snmp/snmpd.conf
The above commands will add a user that can be used for monitoring. Optionally, you can add another user used for management. This is not recommended unless you have a specific reason.
# echo rwcommunity read_write_user >> /etc/snmp/snmpd.conf
SNMP v3 adds security and encrypted authentication/communication. It uses different configuration in /etc/snmp/snmpd.conf, plus additional configuration in /var/net-snmp/snmpd.conf.
# mkdir -p /etc/snmp/ # echo rouser read_only_user >> /etc/snmp/snmpd.conf # mkdir -p /var/net-snmp/ # echo createUser read_only_user SHA password1 AES password2 > /var/net-snmp/snmpd.conf
Note that once snmpd is restarted, /var/net-snmp/snmpd.conf will be rewritten, and the clear-text passwords that you have entered will be encrypted. If this file is modified while snmpd is running, any changes will be reset when the daemon is stopped. Therefore, it is crucial that snmpd is not running while this file is being updated.
The above configuration will suffice for a basic installation. To begin testing, start the snmpd service:
# /etc/rc.d/snmpd start
If using SNMP 1 or 2c, use one of the following commands to test configuration:
# snmpwalk -v 1 -c read_only_user localhost | less # snmpwalk -v 2c -c read_only_user 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 DES -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...
You need to authorize the snmp traffic to income in your machine. Edit the /etc/hosts.allow file and add an entry for the snmpd daemon with the authorized addresses.