In this guide, we are going to learn how to install and configure SNMP on Ubuntu 20.04. SNMP is an acronym for Simple Network Management Protocol. It provides an agentless method of managing and monitoring of network devices and servers for health information, system metrics such as CPU load, Physical Memory usage, number of running processes, service state e.t.c that support polling over the SNMP protocol.. With this method, you don’t need to install the usual Nagios NRPE agent on your hosts.
Installing SNMP on Ubuntu 20.04
Before you can monitor Linux hosts via SNMP using monitoring tools like Nagios or Cacti, you first need to install and configure SNMP.
Install SNMP
The SNMP packages are available on default Ubuntu 20.04 repositories.
You first need to update your package cache;
apt updateOnce the update is done, install SNMP on Ubuntu 20.04.
apt install snmpd snmp libsnmp-dev
Configure SNMP on Ubuntu 20.04
Once the installation is done, proceed to configure SNMP as follows.
The default configuration file for SNMP is /etc/snmp/snmpd.conf. The file is highly commented and thus, we will only make a few changes. As a result, make a copy of the original file before you can proceed.
cp /etc/snmp/snmpd.conf{,.bak}Configuring SNMP Authentication on Ubuntu 20.04
SNMP supports three versions of SNMP protocol;
- SNMP
v1 - SNMP
v2c - SNMP v
3
Both SNMP version 1 and 2c provides authentication using community string, which is a shared secret between the agent and the client that is passed in clear text over the network
SNMP version 3 supports user authentication and message encryption using a variety of protocols and is thus a bit more secure.
Configuring SNMP Version 2c Community on Ubuntu 20.04
As stated above, SNMP v2 provides access using a permission directive, a community string and the source Address. The source address can be IP of the monitoring server such as Nagios Server (SNMP server) or Cacti for example. This directive should be set in the format;
directive community [source [OID]]Where
directivecan berocommunity(provides read-only access) orrwcommunity(provides read-write access)sourcecan be IP of the monitoring server such as Nagios Server (SNMP server) or Cacti for exampleOIDis the optional SNMP tree to provide access to. To configure SNMP v2c
Therefore, edit the snmpd configuration file and configure it to listen on both a localhost and an interface IP. By default, SNMP agent on is set to allow connections originating from the localhost only.
vim /etc/snmp/snmpd.conf
...
###########################################################################
# SECTION: Agent Operating Mode
#
# This section defines how the agent will operate when it
# is running.
...
#agentaddress 127.0.0.1,[::1]
agentAddress udp:127.0.0.1:161,udp:192.168.58.18:161
Also, configure it to allow the monitoring server (Cacti server in my case, with IP, 192.168.58.3) only to connect using the community string (Ex@mPL3).
...
#
SECTION: Access Control Setup
#
This section defines who is allowed to talk to your running
snmp agent.
...
rocommunity Ex@mPL3 192.168.58.3
Save and exit the configuration file.
Note that for any changes to the configuration file to take effect, force the snmpd service to re-read the configuration by running the following command:
systemctl restart snmpdIf you can check, SNMP is now listening on two interfaces;
netstat -nlpu|grep snmpudp 0 0 192.168.58.18:161 0.0.0.0:* 36473/snmpd
udp 0 0 127.0.0.1:161 0.0.0.0:* 36473/snmpdIf firewall is running, allow connection from the monitoring server.
ufw allow from 192.168.58.3 to any port 161 proto udpVerify SNMP v2c Connection with Community String
Next, run the command below from the monitoring server to verify access to the host;
snmpwalk -v2c -c Ex@mPL3 192.168.58.18
iso.3.6.1.2.1.1.1.0 = STRING: "Linux ubuntu20.kifarunix-demo.com 5.4.0-51-generic #56-Ubuntu SMP Mon Oct 5 14:28:49 UTC 2020 x86_64"
iso.3.6.1.2.1.1.2.0 = OID: iso.3.6.1.4.1.8072.3.2.10
iso.3.6.1.2.1.1.3.0 = Timeticks: (2891) 0:00:28.91
iso.3.6.1.2.1.1.4.0 = STRING: "Me <[email protected]>"
iso.3.6.1.2.1.1.5.0 = STRING: "ubuntu20.kifarunix-demo.com"
iso.3.6.1.2.1.1.6.0 = STRING: "Sitting on the Dock of the Bay"
iso.3.6.1.2.1.1.7.0 = INTEGER: 72
iso.3.6.1.2.1.1.8.0 = Timeticks: (2) 0:00:00.02
iso.3.6.1.2.1.1.9.1.2.1 = OID: iso.3.6.1.6.3.10.3.1.1
iso.3.6.1.2.1.1.9.1.2.2 = OID: iso.3.6.1.6.3.11.3.1.1
iso.3.6.1.2.1.1.9.1.2.3 = OID: iso.3.6.1.6.3.15.2.1.1
iso.3.6.1.2.1.1.9.1.2.4 = OID: iso.3.6.1.6.3.1
iso.3.6.1.2.1.1.9.1.2.5 = OID: iso.3.6.1.6.3.16.2.2.1
iso.3.6.1.2.1.1.9.1.2.6 = OID: iso.3.6.1.2.1.49
iso.3.6.1.2.1.1.9.1.2.7 = OID: iso.3.6.1.2.1.4
iso.3.6.1.2.1.1.9.1.2.8 = OID: iso.3.6.1.2.1.50
iso.3.6.1.2.1.1.9.1.2.9 = OID: iso.3.6.1.6.3.13.3.1.3
iso.3.6.1.2.1.1.9.1.2.10 = OID: iso.3.6.1.2.1.92
iso.3.6.1.2.1.1.9.1.3.1 = STRING: "The SNMP Management Architecture MIB."
iso.3.6.1.2.1.1.9.1.3.2 = STRING: "The MIB for Message Processing and Dispatching."
Configure SNMP Version 3 on Ubuntu 20.04
SNMP v3 uses a username, permission, security level, authentication and privacy passphrases to allow access. As a result, you need to create user for authenticating. When created, the user is added to the following configuration files; /etc/snmp/snmpd.conf and /var/lib/net-snmp/snmpd.conf.
Similarly, make a copy of the original configuration file just like we did above.
cp /etc/snmp/snmpd.conf{,.bak}Stop SNMP daemon
systemctl stop snmpdCreate SNMP v3 Authentication User
Create a read-only authentication user using the net-snmp-create-v3-user command. The command syntax is;
net-snmp-create-v3-user [-ro] [-A authpass] [-a MD5|SHA] [-X privpass][-x DES|AES] [username]
net-snmp-create-v3-user -ro -A STrP@SSWRD -a SHA -X STr0ngP@SSWRD -x AES snmpadmin
adding the following line to /var/lib/snmp/snmpd.conf:
createUser snmpadmin SHA "STrP@SSWRD" AES "STr0ngP@SSWRD"
adding the following line to /usr/share/snmp/snmpd.conf:
rouser snmpadmin
Start SNMP daemon and configure inbound Firewall rules to UDP port 161 as we did above.
systemctl start snmpdEnable SNMP daemon to run on system reboot.
systemctl enable snmpdVerify SNMP v3 Connection
Test to verify that everything is working as expected.
snmpwalk -v3 -a SHA -A STrP@SSWRD -x AES -X STr0ngP@SSWRD -l authPriv -u snmpadmin localhost | head
iso.3.6.1.2.1.1.1.0 = STRING: "Linux ubuntu20.kifarunix-demo.com 5.4.0-51-generic #56-Ubuntu SMP Mon Oct 5 14:28:49 UTC 2020 x86_64"
iso.3.6.1.2.1.1.2.0 = OID: iso.3.6.1.4.1.8072.3.2.10
iso.3.6.1.2.1.1.3.0 = Timeticks: (6269) 0:01:02.69
iso.3.6.1.2.1.1.4.0 = STRING: "Me [email protected]"
iso.3.6.1.2.1.1.5.0 = STRING: "ubuntu20.kifarunix-demo.com"
iso.3.6.1.2.1.1.6.0 = STRING: "Sitting on the Dock of the Bay"
iso.3.6.1.2.1.1.7.0 = INTEGER: 72
iso.3.6.1.2.1.1.8.0 = Timeticks: (1) 0:00:00.01
iso.3.6.1.2.1.1.9.1.2.1 = OID: iso.3.6.1.6.3.10.3.1.1
iso.3.6.1.2.1.1.9.1.2.2 = OID: iso.3.6.1.6.3.11.3.1.1
From a remote host;
snmpwalk -v3 -a SHA -A STrP@SSWRD -x AES -X STr0ngP@SSWRD -l authPriv -u snmpadmin 192.168.58.18 | head
iso.3.6.1.2.1.1.1.0 = STRING: "Linux ubuntu20.kifarunix-demo.com 5.4.0-51-generic #56-Ubuntu SMP Mon Oct 5 14:28:49 UTC 2020 x86_64"
iso.3.6.1.2.1.1.2.0 = OID: iso.3.6.1.4.1.8072.3.2.10
iso.3.6.1.2.1.1.3.0 = Timeticks: (11693) 0:01:56.93
iso.3.6.1.2.1.1.4.0 = STRING: "Me <[email protected]>"
iso.3.6.1.2.1.1.5.0 = STRING: "ubuntu20.kifarunix-demo.com"
iso.3.6.1.2.1.1.6.0 = STRING: "Sitting on the Dock of the Bay"
iso.3.6.1.2.1.1.7.0 = INTEGER: 72
iso.3.6.1.2.1.1.8.0 = Timeticks: (1) 0:00:00.01
iso.3.6.1.2.1.1.9.1.2.1 = OID: iso.3.6.1.6.3.10.3.1.1
iso.3.6.1.2.1.1.9.1.2.2 = OID: iso.3.6.1.6.3.11.3.1.1
Great!! You have successfully setup SNMP v2c and SNMP v3 on an Ubuntu 20.04 system. You can now configure your server for polling from a remove monitoring server using SNMP strings or with SNMP v3.
Other Tutorials
Install and Configure SNMP on CentOS 8
Install and Configure SNMP on Debian 10 Buster
How to Configure SNMP version 3 on Debian 9
How to Configure SNMP Version 2c on Debian 9
Nagios SNMP Monitoring of Linux Hosts on AlienVault USM/OSSIM
