Example Net-SNMP setup on Ubuntu

First install Net-SNMP :

root@server:~# apt-get install snmpd

Then make sure the SNMPDOPTS line in /etc/default/snmpd looks like this

SNMPDOPTS='-Lsd -Lf /dev/null -u snmp -p /var/run/snmpd.pid'

Replace the default snmpd.conf file with something like this, changing the community, location and contact fields

com2sec readonly  default         <COMMUNITY>

group MyROGroup v1         readonly
group MyROGroup v2c        readonly
group MyROGroup usm        readonly

view all    included  .1                               80

access MyROGroup ""      any       noauth    exact  all    none   none

syslocation <LOCATION>
syscontact <CONTACT>

# This line allows observer to detect the host OS if the distro script is installed
#exec .1.3.6.1.4.1.2021.7890.1 distro /usr/bin/distro 

You should then be able to restart snmpd

root@server:~# /etc/init.d/snmpd restart

And then add the device to your observer installation!