How to Add Remote Linux Host to Cacti for Monitoring

In the previous guide, we demonstrated how you can install Cacti monitoring server on CentOS 8. This tutorial goes a step further and shows you how you can add and monitor remote Linux hosts on Cacti. We are going to add remote Ubuntu 20.04 LTS and CentOS 8 systems to the cacti server for monitoring.

Let’s begin.

Step 1)  Install SNMP service on Linux hosts

SNMP, short for Simple Network Management Protocol is a protocol used for gathering information about devices in a network. Using SNMP, you can poll metrics such as CPU utilization, memory usage, disk utilization, network bandwidth etc. This information will, later on, be graphed in Cacti to provide an intuitive overview of the remote hosts’ performance.

With that in mind, we are going to install and enable SNMP service on both Linux hosts:

On Ubuntu 20.04

To install snmp agent, run the command:

$ sudo apt install snmp snmpd -y

On CentOS 8

$ sudo dnf install net-snmp net-snmp-utils -y

SNMP starts automatically upon installation. To confirm this, confirm the status by running:

$ sudo systemctl status snmpd

If the service is not running yet, start and enable it on boot as shown:

$ sudo systemctl start snmpd

We can clearly see that the service is up and running. By default, SNMP runs listens on UDP port 161, You can verify this using the netstat command as shown.

$ sudo netstat -pnltu | grep snmpd

netstat-snmp-linux

Step 2) Configuring SNMP service

So far, we have succeeded in installing snmp service and confirmed that it is running as expected. The next course of action is to configure the snmp service so that data can be collected and shipped to the Cacti service.

The configuration file is located at /etc/snmp/snmpd.conf

For Ubuntu 20.04

We need to configure a few parameters. First, locate the sysLocation and sysContact directives. These define your Linux client’s Physical location.

Default-syslocation-syscontact-snmpd-linux

Therefore, feel free to provide your client’s location.

Syslocation-Syscontact-snmpd-ubuntu-20-04

Next, locate the agentaddress directive. This refers to the IP address and the port number that the agent will listen to.

Default-agent-address-snmpd-ubuntu-20-04

Adjust the directive as shown below where 192.168.2.106 is my client system’s address.

agentaddress  udp:192.168.2.106:161

AgentAddress-cacti-server-Ubuntu-20-04

The directive will now allow the system’s local IP to listen to any snmp requests. Next up, add the view directive below above the other view directives:

view     all      included     .1      80

View-Directive-snmpd-Ubuntu-20-04

Next, change the rocommunity attribute shown below

rocommunity  public default -V systemonly
to:
rocommunity  public default -V all

rocommunity-snmpd-linux

Finally, to ensure the snmp service is working as expected, run the command below on the Linux host.

$ sudo snmpwalk -v 1 -c public -O e 192.168.2.106

You should get some massive output as shown.

snmpwalk-command-cacti-ubuntu-20-04

For CentOS 8

In CentOS 8, the configuration is slightly different. First, locate the line that begins with the com2sec  directive as shown:

default-com2sec-directive-snmpd-centos8

We will specify a new security name known as AllUser and delete the notConfigUser as shown:

Update-com2sec-directive-snmpd-centos8

Next, locate the line that starts with the group directive as shown.

Default-Group-directive-snmpd-centos8

We will modify the second attribute and specify AllGroup as the group name and AllUser as the security name as previously defined.Change-group-directive-snmpd-centos8

In the view section, add this line

view    AllView         included        .1

View-Directive-snmpd-centos8

Finally, locate the line beginning with the access directive.

Default-access-directive-snmpd-centos8

Modify it as shown:

Change-access-directive-snmpd-centos8

Save the changes and exit the configuration file. Restart snmpd daemon for the changes to take effect

$ sudo systemctl restart snmpd

Also, enable the service to start on boot.

$ sudo systemctl enable snmpd

Once again, verify if the snmp configuration is working as expected using the snmpwalk command:

$ sudo snmpwalk -v 2c -c public -O e 127.0.0.1

snmpwalk-command-cacti-centos8

Perfect! everything seems to be running as expected.

Step 3) Configure the firewall rules for snmp

Next, we need to open udp port 161 to allow snmp traffic on both the Cacti server and Linux hosts.

For Ubuntu 20.04 host

Run the beneaths commands to allow udp port 161 in firewall,

$ sudo ufw allow 161/udp
$ sudo ufw reload

For CentOS 8 host

For CentOS 8 client and the Cacti server that also runs on CentOS 8, invoke the following commands:

$ sudo firewall-cmd --add-port=161/udp --zone=public --permanent
$ sudo firewall-cmd --reload

Head over to the Cacti server and run the commands shown to confirm that snmp is shipping metrics from the remote clients.

$ sudo snmpwalk -v 1 -c public -O e 192.168.2.106  # Ubuntu
$ sudo snmpwalk -v 2c -c public -O e 192.168.2.104 # CentOS

snmpwalk-from-cacti-server-centos8

Great! This confirms that the Cacti server is receiving system metrics from the remote Linux systems.

Step 4) Adding remote Linux host to Cacti

This is the last section where you have to add your remote Linux hosts. So, log in to the Cacti server and click on ‘Create devices’ as shown.

Create-Device-option-Cacti-Tool

In my case, my Ubuntu remote host was already detected by Cacti and listed as shown.

Auto-detected-remote-ubuntu-machine-cacti

Click on your device and be keen to notice the SNMP information at the very top as shown.

Remote-Ubuntu-snmp-information-Cacti-Toll

Next, scroll down and click on the ‘Save’ button.

Save-snmp-information-remote-ubuntu-cacti-tool

If your device is not listed, simply click on ‘Create’ > ‘Devices’ and fill out the details of your device like in the CentOS8 host as shown.

Create-device-remote-centos8-cacti-tool

Once the device is added, click on the ‘Graphs’ tab.

Graphs-Option-Cacti-Tool-CentOS8

On the next page, select your device’s name

Generate-Graph-Ubuntu-host-Cacti-Tool

Scroll all the way to the bottom and click the ‘Create’ button.

Choose-Create-Option-generate-graphs-cacti-tool

Wait about 10-20 minutes for the graphs to start being populated. Finally, you will start noticing the remote host’s statistics being graphed as shown.

Remote-Ubuntu-host-graphs-Cacti-Tool

And this brings a conclusion to this article. We are glad you were able to follow along the way. Do let us know how it went and we will gladly help out in case of any issues.

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