OpenNMS installation script for Debian and Ubuntu

Add an Ubuntu server

In Ubuntu, install SNMP:

sudo apt install snmp snmpd snmp-mibs-downloader

There are two files that look nearly identical:

/etc/snmp/snmp.conf: This is for the client (the snmpwalk tool). It doesn't understand "agentAddress" or "rocommunity".
/etc/snmp/snmpd.conf: (Note the 'd') This is for the daemon (the background service). This is where your settings belong.

Edit the Daemon Config: Open this file:

sudo vim /etc/snmp/snmpd.conf
Add your configuration there:

agentAddress udp:161,udp6:[::1]:161

rocommunity public 192.168.1.0/24 (Adapt this range according to your network)

(When using a subnet like 192.168.1.0/24, any device on that network, including OpenNMS, can read it.). You can also replace this range with the IP address of your OpenNMS server

After saving the file (Ctrl+O, Enter, Ctrl+X), restart the daemon:

sudo systemctl restart snmpd

If you still get "Timeout," it’s usually one of two things:

The Firewall: Ubuntu’s ufw might be blocking port 161. sudo ufw allow 161/udp

Optional: Add other services like HTTP(S), SSH, (S)FTP, depending of your needs.

Binding Issue: Run netstat -tulpen | grep 161 to make sure the service is actually listening on 0.0.0.0:161 and not just 127.0.0.1.

Restart UFW:

sudo ufw reload

(Or start it with sudo ufw enable if used for the first time)

Run the walk again, but try it locally first to ensure the service is healthy:

snmpwalk -v2c -c public localhost system

If that works, try it from your OpenNMS machine using the Ubuntu IP.